diff --git a/README.md b/README.md
index d21795e596..b661d105a3 100644
--- a/README.md
+++ b/README.md
@@ -52,14 +52,13 @@ To build for standalone use in the browser, install `browserify` and check [run-
   - [`VM` debugging hooks](#vm-debugging-hooks)
     - [`vm.onStep`](#vmonstep)
 
-### `new VM([StateTrie], [blockchain])`
+### `new VM([opts])`
 Creates a new VM object
-- `StateTrie` - The [Patricia Merkle Tree](https://github.com/wanderer/merkle-patricia-tree) that contains the state. If no trie is given the `VM` will create an in memory trie.
-- `blockchain` - an instance of the [`Blockchain`](https://github.com/ethereum/ethereumjs-lib/blob/master/docs/blockchain.md). If no blockchain is given a fake blockchain will be used.
 - `opts`
-  - `state` - the state trie
-  - `blockchain` - an instance of ethereumjs-blockchain
-  - `activatePrecompiles` - create entries in the state tree for the precompiled contracts
+  - `stateManager` - A state manager instance (**EXPERIMENTAL** - unstable API)
+  - `state` - A merkle-patricia-tree instance for the state tree (ignored if `stateManager` is passed)
+  - `blockchain` - A blockchain object for storing/retrieving blocks (ignored if `stateManager` is passed)
+  - `activatePrecompiles` - Create entries in the state tree for the precompiled contracts
 
 ### `VM` methods
 
diff --git a/lib/index.js b/lib/index.js
index 69528f2bd2..9652e5f9a8 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -28,21 +28,27 @@ VM.deps = {
 /**
  * @constructor
  * @param {Object} [opts]
- * @param {Trie} [opts.state] A merkle-patricia-tree instance for the state tree
- * @param {Blockchain} [opts.blockchain] A blockchain object for storing/retrieving blocks
+ * @param {StateManager} [opts.stateManager] A state manager instance (EXPERIMENTAL - unstable API)
+ * @param {Trie} [opts.state] A merkle-patricia-tree instance for the state tree (ignored if stateManager is passed)
+ * @param {Blockchain} [opts.blockchain] A blockchain object for storing/retrieving blocks (ignored if stateManager is passed)
  * @param {Boolean} [opts.activatePrecompiles] Create entries in the state tree for the precompiled contracts
  */
 function VM (opts = {}) {
-  this.stateManager = new StateManager({
-    trie: opts.state,
-    blockchain: opts.blockchain
-  })
+  this.opts = opts
+
+  if (opts.stateManager) {
+    this.stateManager = opts.stateManager
+  } else {
+    this.stateManager = new StateManager({
+      trie: opts.state,
+      blockchain: opts.blockchain
+    })
+  }
 
   // temporary
   // this is here for a gradual transition to StateManager
   this.blockchain = this.stateManager.blockchain
   this.trie = this.stateManager.trie
-  this.opts = opts || {}
 
   // precompiled contracts
   this._precompiled = {}