diff --git a/bin/handleError.js b/bin/handleError.js
index b7cd224..21a100d 100644
--- a/bin/handleError.js
+++ b/bin/handleError.js
@@ -27,6 +27,14 @@ var handlers = {
 
 	DUPLICATE_IMPORT_OPTIONS: function ( err ) {
 		console.error( chalk.red( 'use --input, or pass input path as argument' ) );
+	},
+
+	ROLLUP_WATCH_NOT_INSTALLED: function ( err ) {
+		console.error( chalk.red( 'rollup --watch depends on the rollup-watch package, which could not be found. You can install it globally (recommended) with ' ) + chalk.cyan( 'npm install -g rollup-watch' ) );
+	},
+
+	WATCHER_MISSING_INPUT_OR_OUTPUT: function ( err ) {
+		console.error( chalk.red( 'must specify --input and --output when using rollup --watch' ) );
 	}
 };
 
diff --git a/bin/help.md b/bin/help.md
index 46886c7..7b02ed1 100644
--- a/bin/help.md
+++ b/bin/help.md
@@ -9,6 +9,7 @@ Basic options:
 -h, --help               Show this help message
 -c, --config             Use this config file (if argument is used but value
                            is unspecified, defaults to rollup.config.js)
+-w, --watch              Watch files in bundle and rebuild on changes
 -i, --input              Input (alternative to <entry file>)
 -o, --output <output>    Output (if absent, prints to stdout)
 -f, --format [es6]       Type of output (amd, cjs, es6, iife, umd)
diff --git a/bin/rollup b/bin/rollup
index 200c4bb..123f388 100755
--- a/bin/rollup
+++ b/bin/rollup
@@ -20,7 +20,8 @@ command = minimist( process.argv.slice( 2 ), {
 		n: 'name',
 		o: 'output',
 		u: 'id',
-		v: 'version'
+		v: 'version',
+		w: 'watch'
 	}
 });
 
diff --git a/bin/runRollup.js b/bin/runRollup.js
index ea8ade9..38d5339 100644
--- a/bin/runRollup.js
+++ b/bin/runRollup.js
@@ -1,7 +1,9 @@
 require( 'source-map-support' ).install();
 
 var path = require( 'path' );
+var relative = require( 'require-relative' );
 var handleError = require( './handleError' );
+var chalk = require( 'chalk' );
 var rollup = require( '../' );
 
 // log to stderr to keep `rollup main.js > bundle.js` from breaking
@@ -127,7 +129,43 @@ function execute ( options, command ) {
 	});
 
 	try {
-		bundle( options ).catch( handleError );
+		if ( command.watch ) {
+			if ( !options.entry || !options.dest ) {
+				handleError({ code: 'WATCHER_MISSING_INPUT_OR_OUTPUT' });
+			}
+
+			try {
+				var watch = relative( 'rollup-watch', process.cwd() );
+				var watcher = watch( rollup, options );
+
+				watcher.on( 'event', function ( event ) {
+					switch ( event.code ) {
+						case 'STARTING':
+							console.error( 'checking rollup-watch version...' );
+							break;
+
+						case 'BUILD_START':
+							console.error( 'bundling...' );
+							break;
+
+						case 'BUILD_END':
+							console.error( 'bundled in ' + event.duration + 'ms. Watching for changes...' );
+							break;
+
+						default:
+							console.error( 'unknown event', event );
+					}
+				});
+			} catch ( err ) {
+				if ( err.code === 'MODULE_NOT_FOUND' ) {
+					err.code = 'ROLLUP_WATCH_NOT_INSTALLED';
+				}
+
+				handleError( err );
+			}
+		} else {
+			bundle( options ).catch( handleError );
+		}
 	} catch ( err ) {
 		handleError( err );
 	}
diff --git a/package.json b/package.json
index e6d87b9..dba86ad 100644
--- a/package.json
+++ b/package.json
@@ -63,6 +63,7 @@
   "dependencies": {
     "chalk": "^1.1.1",
     "minimist": "^1.2.0",
+    "require-relative": "^0.8.7",
     "source-map-support": "^0.4.0"
   },
   "files": [