diff --git a/chain/src/txhashset.rs b/chain/src/txhashset.rs
index 3cc28ee04..348fc66e8 100644
--- a/chain/src/txhashset.rs
+++ b/chain/src/txhashset.rs
@@ -869,7 +869,10 @@ impl<'a> Extension<'a> {
 
 		debug!(
 			LOGGER,
-			"txhashset: validated the output|rproof|kernel mmrs, took {}s",
+			"txhashset: validated the output {}, rproof {}, kernel {} mmrs, took {}s",
+			self.output_pmmr.unpruned_size(),
+			self.rproof_pmmr.unpruned_size(),
+			self.kernel_pmmr.unpruned_size(),
 			now.elapsed().as_secs(),
 		);
 
@@ -1224,6 +1227,9 @@ fn input_pos_to_rewind(
 		return Ok(bitmap);
 	}
 
+	//
+	// TODO - rework this loop to use Bitmap::fast_or() on a vec of bitmaps.
+	//
 	loop {
 		if current == block_header.hash() {
 			break;
diff --git a/core/src/core/pmmr.rs b/core/src/core/pmmr.rs
index 03c01c22a..810b0edc1 100644
--- a/core/src/core/pmmr.rs
+++ b/core/src/core/pmmr.rs
@@ -594,6 +594,9 @@ pub fn peak_map_height(mut pos: u64) -> (u64, u64) {
 /// are built.
 
 pub fn bintree_postorder_height(num: u64) -> u64 {
+	if num == 0 {
+		return 0;
+	}
 	peak_map_height(num - 1).1
 }
 
@@ -669,7 +672,13 @@ pub fn family_branch(pos: u64, last_pos: u64) -> Vec<(u64, u64)> {
 	branch
 }
 
-/// Gets the position of the rightmost node (i.e. leaf) relative to the current
-fn bintree_rightmost(num: u64) -> u64 {
+/// Gets the position of the rightmost node (i.e. leaf) beneath the provided subtree root.
+pub fn bintree_rightmost(num: u64) -> u64 {
 	num - bintree_postorder_height(num)
 }
+
+/// Gets the position of the rightmost node (i.e. leaf) beneath the provided subtree root.
+pub fn bintree_leftmost(num: u64) -> u64 {
+	let height = bintree_postorder_height(num);
+	num + 2 - (2 << height)
+}
diff --git a/core/tests/pmmr.rs b/core/tests/pmmr.rs
index 5a1c0e568..e294aacfc 100644
--- a/core/tests/pmmr.rs
+++ b/core/tests/pmmr.rs
@@ -56,6 +56,32 @@ fn first_100_mmr_heights() {
 	}
 }
 
+// The pos of the rightmost leaf for the provided MMR size (last leaf in subtree).
+#[test]
+fn test_bintree_rightmost() {
+	assert_eq!(pmmr::bintree_rightmost(0), 0);
+	assert_eq!(pmmr::bintree_rightmost(1), 1);
+	assert_eq!(pmmr::bintree_rightmost(2), 2);
+	assert_eq!(pmmr::bintree_rightmost(3), 2);
+	assert_eq!(pmmr::bintree_rightmost(4), 4);
+	assert_eq!(pmmr::bintree_rightmost(5), 5);
+	assert_eq!(pmmr::bintree_rightmost(6), 5);
+	assert_eq!(pmmr::bintree_rightmost(7), 5);
+}
+
+// The pos of the leftmost leaf for the provided MMR size (first leaf in subtree).
+#[test]
+fn test_bintree_leftmost() {
+	assert_eq!(pmmr::bintree_leftmost(0), 0);
+	assert_eq!(pmmr::bintree_leftmost(1), 1);
+	assert_eq!(pmmr::bintree_leftmost(2), 2);
+	assert_eq!(pmmr::bintree_leftmost(3), 1);
+	assert_eq!(pmmr::bintree_leftmost(4), 4);
+	assert_eq!(pmmr::bintree_leftmost(5), 5);
+	assert_eq!(pmmr::bintree_leftmost(6), 4);
+	assert_eq!(pmmr::bintree_leftmost(7), 1);
+}
+
 #[test]
 fn test_n_leaves() {
 	// make sure we handle an empty MMR correctly
diff --git a/store/src/pmmr.rs b/store/src/pmmr.rs
index 1d70ba6a7..369aece3c 100644
--- a/store/src/pmmr.rs
+++ b/store/src/pmmr.rs
@@ -157,11 +157,7 @@ where
 	}
 
 	/// Rewind the PMMR backend to the given position.
-	fn rewind(
-		&mut self,
-		position: u64,
-		rewind_rm_pos: &Bitmap,
-	) -> Result<(), String> {
+	fn rewind(&mut self, position: u64, rewind_rm_pos: &Bitmap) -> Result<(), String> {
 		// First rewind the leaf_set with the necessary added and removed positions.
 		if self.prunable {
 			self.leaf_set.rewind(position, rewind_rm_pos);
@@ -224,9 +220,8 @@ where
 	pub fn new(
 		data_dir: String,
 		prunable: bool,
-		header: Option<&BlockHeader>
+		header: Option<&BlockHeader>,
 	) -> io::Result<PMMRBackend<T>> {
-
 		let hash_file = AppendOnlyFile::open(format!("{}/{}", data_dir, PMMR_HASH_FILE))?;
 		let data_file = AppendOnlyFile::open(format!("{}/{}", data_dir, PMMR_DATA_FILE))?;
 
@@ -239,8 +234,8 @@ where
 			LeafSet::copy_snapshot(leaf_set_path.clone(), leaf_snapshot_path.clone())?;
 		}
 
-		let prune_list = PruneList::open(format!("{}/{}", data_dir, PMMR_PRUN_FILE))?;
 		let leaf_set = LeafSet::open(leaf_set_path.clone())?;
+		let prune_list = PruneList::open(format!("{}/{}", data_dir, PMMR_PRUN_FILE))?;
 
 		Ok(PMMRBackend {
 			data_dir,
@@ -303,6 +298,8 @@ where
 				format!("Could not write to log data storage, disk full? {:?}", e),
 			));
 		}
+
+		// Flush the leaf_set to disk.
 		self.leaf_set.flush()?;
 
 		Ok(())
@@ -421,18 +418,12 @@ where
 		Ok(true)
 	}
 
-	fn pos_to_rm(
-		&self,
-		cutoff_pos: u64,
-		rewind_rm_pos: &Bitmap,
-	) -> (Bitmap, Bitmap) {
+	fn pos_to_rm(&self, cutoff_pos: u64, rewind_rm_pos: &Bitmap) -> (Bitmap, Bitmap) {
 		let mut expanded = Bitmap::create();
 
-		let leaf_pos_to_rm = self.leaf_set.removed_pre_cutoff(
-			cutoff_pos,
-			rewind_rm_pos,
-			&self.prune_list,
-		);
+		let leaf_pos_to_rm =
+			self.leaf_set
+				.removed_pre_cutoff(cutoff_pos, rewind_rm_pos, &self.prune_list);
 
 		for x in leaf_pos_to_rm.iter() {
 			expanded.add(x);
diff --git a/store/src/prune_list.rs b/store/src/prune_list.rs
index 5e1b27d3a..331d6230c 100644
--- a/store/src/prune_list.rs
+++ b/store/src/prune_list.rs
@@ -13,8 +13,6 @@
 // limitations under the License.
 
 //! The Grin "Prune List" implementation.
-//! Currently implemented as a vec of u64 positions.
-//! *Soon* to be implemented as a compact bitmap.
 //!
 //! Maintains a set of pruned root node positions that define the pruned
 //! and compacted "gaps" in the MMR data and hash files.
@@ -29,7 +27,9 @@ use std::path::Path;
 
 use croaring::Bitmap;
 
-use core::core::pmmr::{bintree_postorder_height, family, is_leaf, path};
+use core::core::pmmr::{bintree_postorder_height, family, path};
+
+use util::LOGGER;
 
 /// Maintains a list of previously pruned nodes in PMMR, compacting the list as
 /// parents get pruned and allowing checking whether a leaf is pruned. Given
@@ -46,6 +46,10 @@ pub struct PruneList {
 	path: Option<String>,
 	/// Bitmap representing pruned root node positions.
 	bitmap: Bitmap,
+	/// Bitmap representing all pruned node positions (everything under the pruned roots).
+	pruned_cache: Bitmap,
+	shift_cache: Vec<u64>,
+	leaf_shift_cache: Vec<u64>,
 }
 
 unsafe impl Send for PruneList {}
@@ -57,6 +61,9 @@ impl PruneList {
 		PruneList {
 			path: None,
 			bitmap: Bitmap::create(),
+			pruned_cache: Bitmap::create(),
+			shift_cache: vec![],
+			leaf_shift_cache: vec![],
 		}
 	}
 
@@ -72,31 +79,42 @@ impl PruneList {
 			Bitmap::create()
 		};
 
-		Ok(PruneList {
+		let mut prune_list = PruneList {
 			path: Some(path.clone()),
 			bitmap,
-		})
+			pruned_cache: Bitmap::create(),
+			shift_cache: vec![],
+			leaf_shift_cache: vec![],
+		};
+
+		// Now built the shift and pruned caches from the bitmap we read from disk.
+		prune_list.init_caches();
+
+		if !prune_list.bitmap.is_empty() {
+			debug!(LOGGER, "prune_list: bitmap {} pos ({} bytes), pruned_cache {} pos ({} bytes), shift_cache {}, leaf_shift_cache {}",
+				prune_list.bitmap.cardinality(),
+				prune_list.bitmap.get_serialized_size_in_bytes(),
+				prune_list.pruned_cache.cardinality(),
+				prune_list.pruned_cache.get_serialized_size_in_bytes(),
+				prune_list.shift_cache.len(),
+				prune_list.leaf_shift_cache.len(),
+			);
+		}
+
+		Ok(prune_list)
 	}
 
-	fn clear_leaves(&mut self) {
-		let mut leaf_pos = Bitmap::create();
-		for x in self.bitmap.iter() {
-			if is_leaf(x as u64) {
-				leaf_pos.add(x);
-			}
-		}
-		self.bitmap.andnot_inplace(&leaf_pos);
+	fn init_caches(&mut self) {
+		self.build_shift_cache();
+		self.build_leaf_shift_cache();
+		self.build_pruned_cache();
 	}
 
 	/// Save the prune_list to disk.
 	/// Clears out leaf pos before saving to disk
 	/// as we track these via the leaf_set.
 	pub fn flush(&mut self) -> io::Result<()> {
-		// First clear any leaf pos from the prune_list (these are tracked via the
-		// leaf_set).
-		self.clear_leaves();
-
-		// Now run the optimization step on the bitmap.
+		// Run the optimization step on the bitmap.
 		self.bitmap.run_optimize();
 
 		// TODO - consider writing this to disk in a tmp file and then renaming?
@@ -108,12 +126,16 @@ impl PruneList {
 			file.flush()?;
 		}
 
+		// Rebuild our "shift caches" here as we are flushing changes to disk
+		// and the contents of our prune_list has likely changed.
+		self.init_caches();
+
 		Ok(())
 	}
 
 	/// Return the total shift from all entries in the prune_list.
 	pub fn get_total_shift(&self) -> u64 {
-		self.get_shift(self.bitmap.maximum() as u64 + 1)
+		self.get_shift(self.bitmap.maximum() as u64)
 	}
 
 	/// Computes by how many positions a node at pos should be shifted given the
@@ -121,46 +143,87 @@ impl PruneList {
 	/// Note: the node at pos may be pruned and may be compacted away itself and
 	/// the caller needs to be aware of this.
 	pub fn get_shift(&self, pos: u64) -> u64 {
-		let pruned = self.pruned_lte(pos);
+		if self.bitmap.is_empty() {
+			return 0;
+		}
 
-		// skip by the number of leaf nodes pruned in the preceeding subtrees
-		// which just 2^height
-		// except in the case of height==0
-		// (where we want to treat the pruned tree as 0 leaves)
-		pruned
-			.iter()
-			.map(|n| {
-				let height = bintree_postorder_height(*n);
-				// height 0, 1 node, offset 0 = 0 + 0
-				// height 1, 3 nodes, offset 2 = 1 + 1
-				// height 2, 7 nodes, offset 6 = 3 + 3
-				// height 3, 15 nodes, offset 14 = 7 + 7
+		let idx = self.bitmap.rank(pos as u32);
+		if idx == 0 {
+			return 0;
+		}
+
+		if idx > self.shift_cache.len() as u64 {
+			self.shift_cache[self.shift_cache.len() - 1]
+		} else {
+			self.shift_cache[idx as usize - 1]
+		}
+	}
+
+	fn build_shift_cache(&mut self) {
+		if self.bitmap.is_empty() {
+			return;
+		}
+
+		self.shift_cache.clear();
+		for pos in self.bitmap.iter() {
+			let pos = pos as u64;
+			let prev_shift = self.get_shift(pos - 1);
+
+			let curr_shift = if self.is_pruned_root(pos) {
+				let height = bintree_postorder_height(pos);
 				2 * ((1 << height) - 1)
-			})
-			.sum()
+			} else {
+				0
+			};
+
+			self.shift_cache.push(prev_shift + curr_shift);
+		}
 	}
 
 	/// As above, but only returning the number of leaf nodes to skip for a
 	/// given leaf. Helpful if, for instance, data for each leaf is being stored
 	/// separately in a continuous flat-file.
 	pub fn get_leaf_shift(&self, pos: u64) -> u64 {
-		let pruned = self.pruned_lte(pos);
+		if self.bitmap.is_empty() {
+			return 0;
+		}
 
-		// skip by the number of leaf nodes pruned in the preceeding subtrees
-		// which just 2^height
-		// except in the case of height==0
-		// (where we want to treat the pruned tree as 0 leaves)
-		pruned
-			.iter()
-			.map(|&n| {
-				let height = bintree_postorder_height(n);
+		let idx = self.bitmap.rank(pos as u32);
+		if idx == 0 {
+			return 0;
+		}
+
+		if idx > self.leaf_shift_cache.len() as u64 {
+			self.leaf_shift_cache[self.leaf_shift_cache.len() - 1]
+		} else {
+			self.leaf_shift_cache[idx as usize - 1]
+		}
+	}
+
+	fn build_leaf_shift_cache(&mut self) {
+		if self.bitmap.is_empty() {
+			return;
+		}
+
+		self.leaf_shift_cache.clear();
+
+		for pos in self.bitmap.iter() {
+			let pos = pos as u64;
+			let prev_shift = self.get_leaf_shift(pos - 1);
+
+			let curr_shift = if self.is_pruned_root(pos) {
+				let height = bintree_postorder_height(pos);
 				if height == 0 {
 					0
 				} else {
 					1 << height
 				}
-			})
-			.sum()
+			} else {
+				0
+			};
+
+			self.leaf_shift_cache.push(prev_shift + curr_shift);
+		}
 	}
 
 	/// Push the node at the provided position in the prune list. Compacts the
@@ -171,13 +234,13 @@ impl PruneList {
 		loop {
 			let (parent, sibling) = family(current);
 
-			if self.bitmap.contains(sibling as u32) {
+			if self.bitmap.contains(sibling as u32) || self.pruned_cache.contains(sibling as u32) {
+				self.pruned_cache.add(current as u32);
 				self.bitmap.remove(sibling as u32);
 				current = parent;
 			} else {
-				if !self.is_pruned(current) {
-					self.bitmap.add(current as u32);
-				}
+				self.pruned_cache.add(current as u32);
+				self.bitmap.add(current as u32);
 				break;
 			}
 		}
@@ -198,31 +261,29 @@ impl PruneList {
 		self.bitmap.to_vec().into_iter().map(|x| x as u64).collect()
 	}
 
-	/// Checks if the specified position has been pruned,
-	/// either directly (pos contained in the prune list itself)
-	/// or indirectly (pos is beneath a pruned root).
+	/// Is the pos pruned?
+	/// Assumes the pruned_cache is fully built and up to date.
 	pub fn is_pruned(&self, pos: u64) -> bool {
-		if self.is_empty() {
-			return false;
-		}
+		self.pruned_cache.contains(pos as u32)
+	}
 
-		let path = path(pos, self.bitmap.maximum() as u64);
-		path.into_iter().any(|x| self.bitmap.contains(x as u32))
+	fn build_pruned_cache(&mut self) {
+		if self.bitmap.is_empty() {
+			return;
+		}
+		self.pruned_cache = Bitmap::create_with_capacity(self.bitmap.maximum());
+		for pos in 1..(self.bitmap.maximum() + 1) {
+			let path = path(pos as u64, self.bitmap.maximum() as u64);
+			let pruned = path.into_iter().any(|x| self.bitmap.contains(x as u32));
+			if pruned {
+				self.pruned_cache.add(pos as u32)
+			}
+		}
+		self.pruned_cache.run_optimize();
 	}
 
 	/// Is the specified position a root of a pruned subtree?
 	pub fn is_pruned_root(&self, pos: u64) -> bool {
 		self.bitmap.contains(pos as u32)
 	}
-
-	fn pruned_lte(&self, pos: u64) -> Vec<u64> {
-		let mut res = vec![];
-		for x in self.bitmap.iter() {
-			if x > pos as u32 {
-				break;
-			}
-			res.push(x as u64);
-		}
-		res
-	}
 }
diff --git a/store/tests/prune_list.rs b/store/tests/prune_list.rs
index c14f1aa3b..d6330b34d 100644
--- a/store/tests/prune_list.rs
+++ b/store/tests/prune_list.rs
@@ -26,14 +26,18 @@ fn test_is_pruned() {
 	assert_eq!(pl.is_pruned(3), false);
 
 	pl.add(2);
-	assert_eq!(pl.len(), 1);
-	assert_eq!(pl.to_vec(), [2]);
+	pl.flush().unwrap();
+
+	assert_eq!(pl.to_vec(), vec![2]);
 	assert_eq!(pl.is_pruned(1), false);
 	assert_eq!(pl.is_pruned(2), true);
 	assert_eq!(pl.is_pruned(3), false);
 	assert_eq!(pl.is_pruned(4), false);
 
+	pl.add(2);
 	pl.add(1);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 1);
 	assert_eq!(pl.to_vec(), [3]);
 	assert_eq!(pl.is_pruned(1), true);
@@ -42,6 +46,11 @@ fn test_is_pruned() {
 	assert_eq!(pl.is_pruned(4), false);
 
 	pl.add(4);
+
+	// Flushing the prune_list removes any individual leaf positions.
+	// This assumes we will track these outside the prune_list via the leaf_set.
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 2);
 	assert_eq!(pl.to_vec(), [3, 4]);
 	assert_eq!(pl.is_pruned(1), true);
@@ -49,17 +58,6 @@ fn test_is_pruned() {
 	assert_eq!(pl.is_pruned(3), true);
 	assert_eq!(pl.is_pruned(4), true);
 	assert_eq!(pl.is_pruned(5), false);
-
-	// Flushing the prune_list removes any individual leaf positions.
-	// This assumes we will track these outside the prune_list via the leaf_set.
-	pl.flush().unwrap();
-	assert_eq!(pl.len(), 1);
-	assert_eq!(pl.to_vec(), [3]);
-	assert_eq!(pl.is_pruned(1), true);
-	assert_eq!(pl.is_pruned(2), true);
-	assert_eq!(pl.is_pruned(3), true);
-	assert_eq!(pl.is_pruned(4), false);
-	assert_eq!(pl.is_pruned(5), false);
 }
 
 #[test]
@@ -77,7 +75,9 @@ fn test_get_leaf_shift() {
 	// leaves will not shift shift anything
 	// we only start shifting after pruning a parent
 	pl.add(1);
-	assert_eq!(pl.len(), 1);
+	pl.flush().unwrap();
+
+	assert_eq!(pl.to_vec(), vec![1]);
 	assert_eq!(pl.get_leaf_shift(1), 0);
 	assert_eq!(pl.get_leaf_shift(2), 0);
 	assert_eq!(pl.get_leaf_shift(3), 0);
@@ -85,7 +85,10 @@ fn test_get_leaf_shift() {
 
 	// now add the sibling leaf pos (pos 1 and pos 2) which will prune the parent
 	// at pos 3 this in turn will "leaf shift" the leaf at pos 3 by 2
+	pl.add(1);
 	pl.add(2);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 1);
 	assert_eq!(pl.get_leaf_shift(1), 0);
 	assert_eq!(pl.get_leaf_shift(2), 0);
@@ -97,6 +100,8 @@ fn test_get_leaf_shift() {
 	// leaf offset of subsequent pos will be 2
 	// 00100120
 	pl.add(4);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 2);
 	assert_eq!(pl.to_vec(), [3, 4]);
 	assert_eq!(pl.get_leaf_shift(1), 0);
@@ -112,7 +117,10 @@ fn test_get_leaf_shift() {
 	// the two smaller subtrees (pos 3 and pos 6) are rolled up to larger subtree
 	// (pos 7) the leaf offset is now 4 to cover entire subtree containing first
 	// 4 leaves 00100120
+	pl.add(4);
 	pl.add(5);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 1);
 	assert_eq!(pl.to_vec(), [7]);
 	assert_eq!(pl.get_leaf_shift(1), 0);
@@ -132,6 +140,8 @@ fn test_get_leaf_shift() {
 	pl.add(11);
 	pl.add(12);
 	pl.add(4);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.len(), 2);
 	assert_eq!(pl.to_vec(), [6, 13]);
 	assert_eq!(pl.get_leaf_shift(2), 0);
@@ -154,12 +164,17 @@ fn test_get_shift() {
 	// pruning only a leaf node does not shift any subsequent pos
 	// we will only start shifting when a parent can be pruned
 	pl.add(1);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [1]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);
 	assert_eq!(pl.get_shift(3), 0);
 
+	pl.add(1);
 	pl.add(2);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [3]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);
@@ -171,6 +186,8 @@ fn test_get_shift() {
 	// pos 3 is not a leaf and is already in prune list
 	// prune it and check we are still consistent
 	pl.add(3);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [3]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);
@@ -180,6 +197,8 @@ fn test_get_shift() {
 	assert_eq!(pl.get_shift(6), 2);
 
 	pl.add(4);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [3, 4]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);
@@ -188,7 +207,10 @@ fn test_get_shift() {
 	assert_eq!(pl.get_shift(5), 2);
 	assert_eq!(pl.get_shift(6), 2);
 
+	pl.add(4);
 	pl.add(5);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [7]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);
@@ -204,6 +226,8 @@ fn test_get_shift() {
 	for x in 6..1000 {
 		pl.add(x);
 	}
+	pl.flush().unwrap();
+
 	// and check we shift by a large number (hopefully the correct number...)
 	assert_eq!(pl.get_shift(1010), 996);
 
@@ -212,6 +236,8 @@ fn test_get_shift() {
 	pl.add(8);
 	pl.add(5);
 	pl.add(4);
+	pl.flush().unwrap();
+
 	assert_eq!(pl.to_vec(), [6, 10]);
 	assert_eq!(pl.get_shift(1), 0);
 	assert_eq!(pl.get_shift(2), 0);