diff --git a/mempool/mempool.go b/mempool/mempool.go
index 5a629b159..e26302051 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -60,7 +60,7 @@ type Mempool struct {
 	// Keep a cache of already-seen txs.
 	// This reduces the pressure on the proxyApp.
 	cacheMap  map[string]struct{}
-	cacheList *list.List
+	cacheList *list.List // to remove oldest tx when cache gets too big
 }
 
 func NewMempool(config cfg.Config, proxyAppConn proxy.AppConn) *Mempool {
@@ -81,6 +81,7 @@ func NewMempool(config cfg.Config, proxyAppConn proxy.AppConn) *Mempool {
 	return mempool
 }
 
+// consensus must be able to hold lock to safely update
 func (mem *Mempool) Lock() {
 	mem.proxyMtx.Lock()
 }
@@ -89,10 +90,25 @@ func (mem *Mempool) Unlock() {
 	mem.proxyMtx.Unlock()
 }
 
+// Number of transactions in the mempool clist
 func (mem *Mempool) Size() int {
 	return mem.txs.Len()
 }
 
+// Remove all transactions from mempool and cache
+func (mem *Mempool) Flush() {
+	mem.proxyMtx.Lock()
+	defer mem.proxyMtx.Unlock()
+
+	mem.cacheMap = make(map[string]struct{}, cacheSize)
+	mem.cacheList.Init()
+
+	for e := mem.txs.Front(); e != nil; e = e.Next() {
+		mem.txs.Remove(e)
+		e.DetachPrev()
+	}
+}
+
 // Return the first element of mem.txs for peer goroutines to call .NextWait() on.
 // Blocks until txs has elements.
 func (mem *Mempool) TxsFrontWait() *clist.CElement {
@@ -125,6 +141,8 @@ func (mem *Mempool) CheckTx(tx types.Tx, cb func(*tmsp.Response)) (err error) {
 	if mem.cacheList.Len() >= cacheSize {
 		popped := mem.cacheList.Front()
 		poppedTx := popped.Value.(types.Tx)
+		// NOTE: the tx may have already been removed from the map
+		// but deleting a non-existant element is fine
 		delete(mem.cacheMap, string(poppedTx))
 		mem.cacheList.Remove(popped)
 	}
@@ -146,6 +164,7 @@ func (mem *Mempool) CheckTx(tx types.Tx, cb func(*tmsp.Response)) (err error) {
 
 func (mem *Mempool) removeTxFromCacheMap(tx []byte) {
 	mem.proxyMtx.Lock()
+	// NOTE tx not removed from cacheList
 	delete(mem.cacheMap, string(tx))
 	mem.proxyMtx.Unlock()
 
diff --git a/rpc/core/mempool.go b/rpc/core/mempool.go
index f915ce426..cf3ec919c 100644
--- a/rpc/core/mempool.go
+++ b/rpc/core/mempool.go
@@ -46,7 +46,7 @@ func BroadcastTxSync(tx types.Tx) (*ctypes.ResultBroadcastTx, error) {
 // Else, block until the tx is included in a block,
 //	and return the result of AppendTx (with no error).
 // Even if AppendTx fails, so long as the tx is included in a block this function
-//	will not return an error.
+//	will not return an error - it is the caller's responsibility to check res.Code.
 // The function times out after five minutes and returns the result of CheckTx and an error.
 // TODO: smarter timeout logic or someway to cancel (tx not getting committed is a sign of a larger problem!)
 func BroadcastTxCommit(tx types.Tx) (*ctypes.ResultBroadcastTx, error) {
diff --git a/rpc/test/client_test.go b/rpc/test/client_test.go
index a5b243bea..bb66965ed 100644
--- a/rpc/test/client_test.go
+++ b/rpc/test/client_test.go
@@ -1,11 +1,13 @@
 package rpctest
 
 import (
+	"bytes"
 	"fmt"
 	"testing"
 
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
+	tmsp "github.com/tendermint/tmsp/types"
 )
 
 //--------------------------------------------------------------------------------
@@ -42,33 +44,84 @@ func testStatus(t *testing.T, statusI interface{}) {
 	}
 }
 
-// TODO
-/*
-func testBroadcastTx(t *testing.T, typ string) {
-	amt := int64(100)
-	toAddr := user[1].Address
-	tx := makeDefaultSendTxSigned(t, typ, toAddr, amt)
-	receipt := broadcastTx(t, typ, tx)
-	if receipt.CreatesContract > 0 {
-		t.Fatal("This tx does not create a contract")
-	}
-	if len(receipt.TxHash) == 0 {
-		t.Fatal("Failed to compute tx hash")
-	}
-	pool := node.MempoolReactor().Mempool
-	txs := pool.GetProposalTxs()
-	if len(txs) != mempoolCount {
-		t.Fatalf("The mem pool has %d txs. Expected %d", len(txs), mempoolCount)
-	}
-	tx2 := txs[mempoolCount-1].(*types.SendTx)
-	n, err := new(int64), new(error)
-	buf1, buf2 := new(bytes.Buffer), new(bytes.Buffer)
-	tx.WriteSignBytes(chainID, buf1, n, err)
-	tx2.WriteSignBytes(chainID, buf2, n, err)
-	if bytes.Compare(buf1.Bytes(), buf2.Bytes()) != 0 {
-		t.Fatal("inconsistent hashes for mempool tx and sent tx")
+//--------------------------------------------------------------------------------
+// broadcast tx sync
+
+var testTx = []byte{0x1, 0x2, 0x3, 0x4, 0x5}
+
+func TestURIBroadcastTxSync(t *testing.T) {
+	config.Set("block_size", 0)
+	defer config.Set("block_size", -1)
+	tmResult := new(ctypes.TMResult)
+	_, err := clientURI.Call("broadcast_tx_sync", map[string]interface{}{"tx": testTx}, tmResult)
+	if err != nil {
+		t.Fatal(err)
 	}
-}*/
+	testBroadcastTxSync(t, tmResult)
+}
+
+func TestJSONBroadcastTxSync(t *testing.T) {
+	config.Set("block_size", 0)
+	defer config.Set("block_size", -1)
+	tmResult := new(ctypes.TMResult)
+	_, err := clientJSON.Call("broadcast_tx_sync", []interface{}{testTx}, tmResult)
+	if err != nil {
+		t.Fatal(err)
+	}
+	testBroadcastTxSync(t, tmResult)
+}
+
+func testBroadcastTxSync(t *testing.T, resI interface{}) {
+	tmRes := resI.(*ctypes.TMResult)
+	res := (*tmRes).(*ctypes.ResultBroadcastTx)
+	if res.Code != tmsp.CodeType_OK {
+		t.Fatalf("BroadcastTxSync got non-zero exit code: %v. %X; %s", res.Code, res.Data, res.Log)
+	}
+	mem := node.MempoolReactor().Mempool
+	if mem.Size() != 1 {
+		t.Fatalf("Mempool size should have been 1. Got %d", mem.Size())
+	}
+
+	txs := mem.Reap(1)
+	if !bytes.Equal(txs[0], testTx) {
+		t.Fatalf("Tx in mempool does not match test tx. Got %X, expected %X", txs[0], testTx)
+	}
+
+	mem.Flush()
+}
+
+//--------------------------------------------------------------------------------
+// broadcast tx commit
+
+func TestURIBroadcastTxCommit(t *testing.T) {
+	tmResult := new(ctypes.TMResult)
+	_, err := clientURI.Call("broadcast_tx_commit", map[string]interface{}{"tx": testTx}, tmResult)
+	if err != nil {
+		t.Fatal(err)
+	}
+	testBroadcastTxCommit(t, tmResult)
+}
+
+func TestJSONBroadcastTxCommit(t *testing.T) {
+	tmResult := new(ctypes.TMResult)
+	_, err := clientJSON.Call("broadcast_tx_commit", []interface{}{testTx}, tmResult)
+	if err != nil {
+		t.Fatal(err)
+	}
+	testBroadcastTxCommit(t, tmResult)
+}
+
+func testBroadcastTxCommit(t *testing.T, resI interface{}) {
+	tmRes := resI.(*ctypes.TMResult)
+	res := (*tmRes).(*ctypes.ResultBroadcastTx)
+	if res.Code != tmsp.CodeType_OK {
+		t.Fatalf("BroadcastTxCommit got non-zero exit code: %v. %X; %s", res.Code, res.Data, res.Log)
+	}
+	mem := node.MempoolReactor().Mempool
+	if mem.Size() != 0 {
+		t.Fatalf("Mempool size should have been 0. Got %s", mem.Size())
+	}
+}
 
 //--------------------------------------------------------------------------------
 // Test the websocket service
diff --git a/rpc/test/helpers.go b/rpc/test/helpers.go
index c209324b6..3713aa821 100644
--- a/rpc/test/helpers.go
+++ b/rpc/test/helpers.go
@@ -20,7 +20,6 @@ import (
 var (
 	config            cfg.Config
 	node              *nm.Node
-	mempoolCount      = 0
 	chainID           string
 	rpcAddr           string
 	requestAddr       string