diff --git a/glide.lock b/glide.lock
index b3a182bb3..589b083c7 100644
--- a/glide.lock
+++ b/glide.lock
@@ -136,7 +136,7 @@ imports:
   - data
   - data/base58
 - name: github.com/tendermint/iavl
-  version: 03e6c011329bce607eed69d60737c899519f1f70
+  version: ab22235a11524125a1df019e7b223d9797a88810
 - name: github.com/tendermint/light-client
   version: 76313d625e662ed7b284d066d68ff71edd7a9fac
   subpackages:
diff --git a/store/iavlstore.go b/store/iavlstore.go
index bb7c6d03f..772d3d0e8 100644
--- a/store/iavlstore.go
+++ b/store/iavlstore.go
@@ -1,20 +1,17 @@
 package store
 
 import (
-	"path"
-	"path/filepath"
-	"strings"
-
-	"github.com/pkg/errors"
+	"bytes"
+	"sync"
 
 	"github.com/tendermint/iavl"
 	dbm "github.com/tendermint/tmlibs/db"
 )
 
 // NewIAVLStoreLoader returns a CommitStoreLoader that returns an iavlStore
-func NewIAVLStoreLoader(dbName string, cacheSize int, numHistory int64) CommitStoreLoader {
+func NewIAVLStoreLoader(db dbm.DB, cacheSize int, numHistory int64) CommitStoreLoader {
 	l := iavlStoreLoader{
-		dbName:     dbName,
+		db:         db,
 		cacheSize:  cacheSize,
 		numHistory: numHistory,
 	}
@@ -54,7 +51,7 @@ func (st *iavlStore) Commit() CommitID {
 	}
 
 	// Release an old version of history
-	if st.numHistory < st.tree.Version() {
+	if st.numHistory < st.tree.Version64() {
 		toRelease := version - st.numHistory
 		st.tree.DeleteVersion(toRelease)
 	}
@@ -66,7 +63,12 @@ func (st *iavlStore) Commit() CommitID {
 }
 
 // CacheWrap implements IterKVStore.
-func (st *iavlStore) CacheWrap() CacheWriter {
+func (st *iavlStore) CacheWrap() CacheWrap {
+	return st.CacheIterKVStore()
+}
+
+// CacheKVStore implements IterKVStore.
+func (st *iavlStore) CacheKVStore() CacheKVStore {
 	return st.CacheIterKVStore()
 }
 
@@ -101,68 +103,204 @@ func (st *iavlStore) Remove(key []byte) (prev []byte, removed bool) {
 
 // Iterator implements IterKVStore.
 func (st *iavlStore) Iterator(start, end []byte) Iterator {
-	// XXX Create iavlIterator (without modifying tendermint/iavl)
-	return nil
+	return newIAVLIterator(st.tree.Tree(), start, end, true)
 }
 
 // ReverseIterator implements IterKVStore.
 func (st *iavlStore) ReverseIterator(start, end []byte) Iterator {
-	// XXX Create iavlIterator (without modifying tendermint/iavl)
-	return nil
+	return newIAVLIterator(st.tree.Tree(), start, end, false)
 }
 
 // First implements IterKVStore.
-func (is IAVLStore) First(start, end []byte) (kv KVPair, ok bool) {
-	// XXX
-	return KVPair{}, false
+func (st *iavlStore) First(start, end []byte) (kv KVPair, ok bool) {
+	iter := st.Iterator(start, end)
+	if !iter.Valid() {
+		return kv, false
+	}
+	defer iter.Release()
+	return KVPair{iter.Key(), iter.Value()}, true
 }
 
 // Last implements IterKVStore.
-func (is IAVLStore) Last(start, end []byte) (kv KVPair, ok bool) {
-	// XXX
-	return KVPair{}, false
+func (st *iavlStore) Last(start, end []byte) (kv KVPair, ok bool) {
+	iter := st.ReverseIterator(end, start)
+	if !iter.Valid() {
+		if v, ok := st.Get(start); ok {
+			return KVPair{cp(start), cp(v)}, true
+		} else {
+			return kv, false
+		}
+	}
+	defer iter.Release()
+
+	if bytes.Equal(iter.Key(), end) {
+		// Skip this one, end is exclusive.
+		iter.Next()
+		if !iter.Valid() {
+			return kv, false
+		}
+	}
+
+	return KVPair{iter.Key(), iter.Value()}, true
 }
 
 //----------------------------------------
 
 type iavlIterator struct {
-	// TODO
+	// Underlying store
+	tree *iavl.Tree
+
+	// Domain
+	start, end []byte
+
+	// Iteration order
+	ascending bool
+
+	// Channel to push iteration values.
+	iterCh chan KVPair
+
+	// Close this to release goroutine.
+	quitCh chan struct{}
+
+	// Close this to signal that state is initialized.
+	initCh chan struct{}
+
+	//----------------------------------------
+	// What follows are mutable state.
+	mtx sync.Mutex
+
+	invalid bool   // True once, true forever
+	key     []byte // The current key
+	value   []byte // The current value
 }
 
 var _ Iterator = (*iavlIterator)(nil)
 
+// newIAVLIterator will create a new iavlIterator.
+// CONTRACT: Caller must release the iavlIterator, as each one creates a new
+// goroutine.
+func newIAVLIterator(t *iavl.Tree, start, end []byte, ascending bool) *iavlIterator {
+	itr := &iavlIterator{
+		tree:      t,
+		start:     cp(start),
+		end:       cp(end),
+		ascending: ascending,
+		iterCh:    make(chan KVPair, 0), // Set capacity > 0?
+		quitCh:    make(chan struct{}),
+		initCh:    make(chan struct{}),
+	}
+	go itr.iterateRoutine()
+	go itr.initRoutine()
+	return itr
+}
+
+// Run this to funnel items from the tree to iterCh.
+func (ii *iavlIterator) iterateRoutine() {
+	ii.tree.IterateRange(
+		ii.start, ii.end, ii.ascending,
+		func(key, value []byte) bool {
+			select {
+			case <-ii.quitCh:
+				return true // done with iteration.
+			case ii.iterCh <- KVPair{key, value}:
+				return false // yay.
+			}
+		},
+	)
+	close(ii.iterCh) // done.
+}
+
+// Run this to fetch the first item.
+func (ii *iavlIterator) initRoutine() {
+	ii.receiveNext()
+	close(ii.initCh)
+}
+
 // Domain implements Iterator
 func (ii *iavlIterator) Domain() (start, end []byte) {
-	// TODO
-	return nil, nil
+	return ii.start, ii.end
 }
 
 // Valid implements Iterator
 func (ii *iavlIterator) Valid() bool {
-	// TODO
-	return false
+	ii.waitInit()
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+
+	return !ii.invalid
 }
 
 // Next implements Iterator
 func (ii *iavlIterator) Next() {
-	// TODO
+	ii.waitInit()
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+	ii.assertIsValid()
+
+	ii.receiveNext()
 }
 
 // Key implements Iterator
 func (ii *iavlIterator) Key() []byte {
-	// TODO
-	return nil
+	ii.waitInit()
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+	ii.assertIsValid()
+
+	return ii.key
 }
 
 // Value implements Iterator
 func (ii *iavlIterator) Value() []byte {
-	// TODO
-	return nil
+	ii.waitInit()
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+	ii.assertIsValid()
+
+	return ii.value
 }
 
 // Release implements Iterator
 func (ii *iavlIterator) Release() {
-	// TODO
+	close(ii.quitCh)
+}
+
+//----------------------------------------
+
+func (ii *iavlIterator) setNext(key, value []byte) {
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+	ii.assertIsValid()
+
+	ii.key = key
+	ii.value = value
+}
+
+func (ii *iavlIterator) setInvalid() {
+	ii.mtx.Lock()
+	defer ii.mtx.Unlock()
+	ii.assertIsValid()
+
+	ii.invalid = true
+}
+
+func (ii *iavlIterator) waitInit() {
+	<-ii.initCh
+}
+
+func (ii *iavlIterator) receiveNext() {
+	kvPair, ok := <-ii.iterCh
+	if ok {
+		ii.setNext(kvPair.Key, kvPair.Value)
+	} else {
+		ii.setInvalid()
+	}
+}
+
+func (ii *iavlIterator) assertIsValid() {
+	if ii.invalid {
+		panic("invalid iterator")
+	}
 }
 
 //----------------------------------------
@@ -175,7 +313,7 @@ type iavlStoreLoader struct {
 }
 
 // Load implements CommitLoader.
-func (isl iavlLoader) Load(id CommitID) (CommitStore, error) {
+func (isl iavlStoreLoader) Load(id CommitID) (CommitStore, error) {
 	tree := iavl.NewVersionedTree(isl.db, isl.cacheSize)
 	err := tree.Load()
 	if err != nil {
@@ -184,3 +322,11 @@ func (isl iavlLoader) Load(id CommitID) (CommitStore, error) {
 	store := newIAVLStore(tree, isl.numHistory)
 	return store, nil
 }
+
+//----------------------------------------
+
+func cp(bz []byte) (ret []byte) {
+	ret = make([]byte, len(bz))
+	copy(ret, bz)
+	return ret
+}
diff --git a/store/types.go b/store/types.go
index 22e42ee7f..2e17f6525 100644
--- a/store/types.go
+++ b/store/types.go
@@ -79,7 +79,11 @@ type IterKVStore interface {
 	Iterator(start, end []byte) Iterator
 	ReverseIterator(start, end []byte) Iterator
 
+	// Gets the first item.
 	First(start, end []byte) (kv KVPair, ok bool)
+
+	// Gets the last item (towards "end").
+	// End is exclusive.
 	Last(start, end []byte) (kv KVPair, ok bool)
 
 	// CacheIterKVStore() wraps a thing with a cache.