diff --git a/rpc/client/httpclient.go b/rpc/client/httpclient.go
index 04595e766..88a592348 100644
--- a/rpc/client/httpclient.go
+++ b/rpc/client/httpclient.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/pkg/errors"
+	data "github.com/tendermint/go-data"
 	events "github.com/tendermint/go-events"
 	"github.com/tendermint/go-rpc/client"
 	wire "github.com/tendermint/go-wire"
@@ -67,7 +68,7 @@ func (c *HTTP) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return (*tmResult).(*ctypes.ResultABCIInfo), nil
 }
 
-func (c *HTTP) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (c *HTTP) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	tmResult := new(ctypes.TMResult)
 	_, err := c.rpc.Call("abci_query",
 		map[string]interface{}{"path": path, "data": data, "prove": prove},
diff --git a/rpc/client/interface.go b/rpc/client/interface.go
index 2ba890798..eb79db8b1 100644
--- a/rpc/client/interface.go
+++ b/rpc/client/interface.go
@@ -20,6 +20,7 @@ implementation.
 package client
 
 import (
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
 )
@@ -30,7 +31,7 @@ import (
 type ABCIClient interface {
 	// reading from abci app
 	ABCIInfo() (*ctypes.ResultABCIInfo, error)
-	ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error)
+	ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error)
 
 	// writing to abci app
 	BroadcastTxCommit(tx types.Tx) (*ctypes.ResultBroadcastTxCommit, error)
diff --git a/rpc/client/localclient.go b/rpc/client/localclient.go
index d0f0d11b1..74051d8c9 100644
--- a/rpc/client/localclient.go
+++ b/rpc/client/localclient.go
@@ -1,6 +1,7 @@
 package client
 
 import (
+	data "github.com/tendermint/go-data"
 	nm "github.com/tendermint/tendermint/node"
 	"github.com/tendermint/tendermint/rpc/core"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
@@ -56,7 +57,7 @@ func (c Local) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return core.ABCIInfo()
 }
 
-func (c Local) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (c Local) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	return core.ABCIQuery(path, data, prove)
 }
 
diff --git a/rpc/client/mock/abci.go b/rpc/client/mock/abci.go
index 6f6fa1d47..6a9fe6bdf 100644
--- a/rpc/client/mock/abci.go
+++ b/rpc/client/mock/abci.go
@@ -2,6 +2,7 @@ package mock
 
 import (
 	abci "github.com/tendermint/abci/types"
+	data "github.com/tendermint/go-data"
 	"github.com/tendermint/tendermint/rpc/client"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
@@ -22,7 +23,7 @@ func (a ABCIApp) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return &ctypes.ResultABCIInfo{a.App.Info()}, nil
 }
 
-func (a ABCIApp) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (a ABCIApp) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	q := a.App.Query(abci.RequestQuery{data, path, 0, prove})
 	return &ctypes.ResultABCIQuery{q}, nil
 }
@@ -79,7 +80,7 @@ func (m ABCIMock) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return &ctypes.ResultABCIInfo{res.(abci.ResponseInfo)}, nil
 }
 
-func (m ABCIMock) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (m ABCIMock) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	res, err := m.Query.GetResponse(QueryArgs{path, data, prove})
 	if err != nil {
 		return nil, err
@@ -131,7 +132,7 @@ func (r *ABCIRecorder) _assertABCIClient() client.ABCIClient {
 
 type QueryArgs struct {
 	Path  string
-	Data  []byte
+	Data  data.Bytes
 	Prove bool
 }
 
@@ -149,7 +150,7 @@ func (r *ABCIRecorder) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return res, err
 }
 
-func (r *ABCIRecorder) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (r *ABCIRecorder) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	res, err := r.Client.ABCIQuery(path, data, prove)
 	r.addCall(Call{
 		Name:     "abci_query",
diff --git a/rpc/client/mock/abci_test.go b/rpc/client/mock/abci_test.go
index 823752caf..bb3a734a7 100644
--- a/rpc/client/mock/abci_test.go
+++ b/rpc/client/mock/abci_test.go
@@ -10,6 +10,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"github.com/tendermint/abci/example/dummy"
 	abci "github.com/tendermint/abci/types"
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
 
@@ -35,8 +36,8 @@ func TestABCIMock(t *testing.T) {
 		BroadcastCommit: mock.Call{
 			Args: goodTx,
 			Response: &ctypes.ResultBroadcastTxCommit{
-				CheckTx:   &abci.ResponseCheckTx{Data: []byte("stand")},
-				DeliverTx: &abci.ResponseDeliverTx{Data: []byte("deliver")},
+				CheckTx:   &abci.ResponseCheckTx{Data: data.Bytes("stand")},
+				DeliverTx: &abci.ResponseDeliverTx{Data: data.Bytes("deliver")},
 			},
 			Error: errors.New("bad tx"),
 		},
@@ -91,7 +92,7 @@ func TestABCIRecorder(t *testing.T) {
 	require.Equal(0, len(r.Calls))
 
 	r.ABCIInfo()
-	r.ABCIQuery("path", []byte("data"), true)
+	r.ABCIQuery("path", data.Bytes("data"), true)
 	require.Equal(2, len(r.Calls))
 
 	info := r.Calls[0]
@@ -163,7 +164,7 @@ func TestABCIApp(t *testing.T) {
 	assert.True(res.DeliverTx.Code.IsOK())
 
 	// check the key
-	qres, err := m.ABCIQuery("/key", []byte(key), false)
+	qres, err := m.ABCIQuery("/key", data.Bytes(key), false)
 	require.Nil(err)
 	assert.EqualValues(value, qres.Response.Value)
 }
diff --git a/rpc/client/mock/client.go b/rpc/client/mock/client.go
index a3cecfca1..478862380 100644
--- a/rpc/client/mock/client.go
+++ b/rpc/client/mock/client.go
@@ -16,6 +16,7 @@ package mock
 import (
 	"reflect"
 
+	data "github.com/tendermint/go-data"
 	"github.com/tendermint/tendermint/rpc/client"
 	"github.com/tendermint/tendermint/rpc/core"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
@@ -83,7 +84,7 @@ func (c Client) ABCIInfo() (*ctypes.ResultABCIInfo, error) {
 	return core.ABCIInfo()
 }
 
-func (c Client) ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func (c Client) ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	return core.ABCIQuery(path, data, prove)
 }
 
diff --git a/rpc/client/mock/status_test.go b/rpc/client/mock/status_test.go
index 3e695cd57..12edc8af0 100644
--- a/rpc/client/mock/status_test.go
+++ b/rpc/client/mock/status_test.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 
 	"github.com/tendermint/tendermint/rpc/client/mock"
@@ -16,8 +17,8 @@ func TestStatus(t *testing.T) {
 	m := &mock.StatusMock{
 		Call: mock.Call{
 			Response: &ctypes.ResultStatus{
-				LatestBlockHash:   []byte("block"),
-				LatestAppHash:     []byte("app"),
+				LatestBlockHash:   data.Bytes("block"),
+				LatestAppHash:     data.Bytes("app"),
 				LatestBlockHeight: 10,
 			}},
 	}
diff --git a/rpc/core/abci.go b/rpc/core/abci.go
index 957727267..47b599ada 100644
--- a/rpc/core/abci.go
+++ b/rpc/core/abci.go
@@ -2,12 +2,13 @@ package core
 
 import (
 	abci "github.com/tendermint/abci/types"
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 )
 
 //-----------------------------------------------------------------------------
 
-func ABCIQuery(path string, data []byte, prove bool) (*ctypes.ResultABCIQuery, error) {
+func ABCIQuery(path string, data data.Bytes, prove bool) (*ctypes.ResultABCIQuery, error) {
 	resQuery, err := proxyAppQuery.QuerySync(abci.RequestQuery{
 		Path:  path,
 		Data:  data,
diff --git a/rpc/core/mempool.go b/rpc/core/mempool.go
index 4da83a1f6..358671635 100644
--- a/rpc/core/mempool.go
+++ b/rpc/core/mempool.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	abci "github.com/tendermint/abci/types"
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
 )
@@ -84,7 +85,7 @@ func BroadcastTxCommit(tx types.Tx) (*ctypes.ResultBroadcastTxCommit, error) {
 			Data: deliverTxRes.Data,
 			Log:  deliverTxRes.Log,
 		}
-		log.Notice("DeliverTx passed ", "tx", []byte(tx), "response", deliverTxR)
+		log.Notice("DeliverTx passed ", "tx", data.Bytes(tx), "response", deliverTxR)
 		return &ctypes.ResultBroadcastTxCommit{
 			CheckTx:   checkTxR,
 			DeliverTx: deliverTxR,
diff --git a/rpc/core/routes.go b/rpc/core/routes.go
index 38e609601..58b464208 100644
--- a/rpc/core/routes.go
+++ b/rpc/core/routes.go
@@ -1,9 +1,11 @@
 package core
 
 import (
+	data "github.com/tendermint/go-data"
 	rpc "github.com/tendermint/go-rpc/server"
 	"github.com/tendermint/go-rpc/types"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
+	"github.com/tendermint/tendermint/types"
 )
 
 // TODO: better system than "unsafe" prefix
@@ -104,19 +106,19 @@ func TxResult(hash []byte, prove bool) (ctypes.TMResult, error) {
 	return Tx(hash, prove)
 }
 
-func BroadcastTxCommitResult(tx []byte) (ctypes.TMResult, error) {
+func BroadcastTxCommitResult(tx types.Tx) (ctypes.TMResult, error) {
 	return BroadcastTxCommit(tx)
 }
 
-func BroadcastTxSyncResult(tx []byte) (ctypes.TMResult, error) {
+func BroadcastTxSyncResult(tx types.Tx) (ctypes.TMResult, error) {
 	return BroadcastTxSync(tx)
 }
 
-func BroadcastTxAsyncResult(tx []byte) (ctypes.TMResult, error) {
+func BroadcastTxAsyncResult(tx types.Tx) (ctypes.TMResult, error) {
 	return BroadcastTxAsync(tx)
 }
 
-func ABCIQueryResult(path string, data []byte, prove bool) (ctypes.TMResult, error) {
+func ABCIQueryResult(path string, data data.Bytes, prove bool) (ctypes.TMResult, error) {
 	return ABCIQuery(path, data, prove)
 }
 
diff --git a/rpc/core/status.go b/rpc/core/status.go
index 96ed46ea6..d7d503802 100644
--- a/rpc/core/status.go
+++ b/rpc/core/status.go
@@ -1,6 +1,7 @@
 package core
 
 import (
+	data "github.com/tendermint/go-data"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	"github.com/tendermint/tendermint/types"
 )
@@ -9,8 +10,8 @@ func Status() (*ctypes.ResultStatus, error) {
 	latestHeight := blockStore.Height()
 	var (
 		latestBlockMeta *types.BlockMeta
-		latestBlockHash []byte
-		latestAppHash   []byte
+		latestBlockHash data.Bytes
+		latestAppHash   data.Bytes
 		latestBlockTime int64
 	)
 	if latestHeight != 0 {
diff --git a/rpc/core/types/responses.go b/rpc/core/types/responses.go
index 7cab8535d..59fa09aa0 100644
--- a/rpc/core/types/responses.go
+++ b/rpc/core/types/responses.go
@@ -5,6 +5,7 @@ import (
 
 	abci "github.com/tendermint/abci/types"
 	"github.com/tendermint/go-crypto"
+	data "github.com/tendermint/go-data"
 	"github.com/tendermint/go-p2p"
 	"github.com/tendermint/go-rpc/types"
 	"github.com/tendermint/go-wire"
@@ -34,8 +35,8 @@ type ResultCommit struct {
 type ResultStatus struct {
 	NodeInfo          *p2p.NodeInfo `json:"node_info"`
 	PubKey            crypto.PubKey `json:"pub_key"`
-	LatestBlockHash   []byte        `json:"latest_block_hash"`
-	LatestAppHash     []byte        `json:"latest_app_hash"`
+	LatestBlockHash   data.Bytes    `json:"latest_block_hash"`
+	LatestAppHash     data.Bytes    `json:"latest_app_hash"`
 	LatestBlockHeight int           `json:"latest_block_height"`
 	LatestBlockTime   int64         `json:"latest_block_time"` // nano
 }
@@ -81,7 +82,7 @@ type ResultDumpConsensusState struct {
 
 type ResultBroadcastTx struct {
 	Code abci.CodeType `json:"code"`
-	Data []byte        `json:"data"`
+	Data data.Bytes    `json:"data"`
 	Log  string        `json:"log"`
 
 	Hash []byte `json:"hash"`
diff --git a/rpc/test/client_test.go b/rpc/test/client_test.go
index 50e326050..a9792b5be 100644
--- a/rpc/test/client_test.go
+++ b/rpc/test/client_test.go
@@ -12,6 +12,7 @@ import (
 	"github.com/stretchr/testify/require"
 	abci "github.com/tendermint/abci/types"
 	. "github.com/tendermint/go-common"
+	data "github.com/tendermint/go-data"
 	rpc "github.com/tendermint/go-rpc/client"
 	"github.com/tendermint/tendermint/rpc/core"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
@@ -85,10 +86,10 @@ func testBroadcastTxSync(t *testing.T, client rpc.HTTPClient) {
 //--------------------------------------------------------------------------------
 // query
 
-func testTxKV(t *testing.T) ([]byte, []byte, []byte) {
+func testTxKV(t *testing.T) ([]byte, []byte, types.Tx) {
 	k := randBytes(t)
 	v := randBytes(t)
-	return k, v, []byte(Fmt("%s=%s", k, v))
+	return k, v, types.Tx(Fmt("%s=%s", k, v))
 }
 
 func sendTx(t *testing.T, client rpc.HTTPClient) ([]byte, []byte) {
@@ -114,8 +115,6 @@ func testABCIQuery(t *testing.T, client rpc.HTTPClient) {
 	_, err := client.Call("abci_query",
 		map[string]interface{}{"path": "", "data": k, "prove": false}, tmResult)
 	require.Nil(t, err)
-
-	resQuery := (*tmResult).(*ctypes.ResultABCIQuery)
 	require.EqualValues(t, 0, resQuery.Response.Code)
 
 	// XXX: specific to value returned by the dummy