diff --git a/bin/run.js b/bin/run.js
index 4c171e8..279b9f8 100755
--- a/bin/run.js
+++ b/bin/run.js
@@ -15,6 +15,13 @@ const agentPool = require('../lib/agentPool.js');
 const test262Finder = require('../lib/findTest262.js');
 const scenariosForTest = require('../lib/scenarios.js');
 
+// test262 directory (used to locate includes unless overridden with includesDir)
+let test262Dir = argv.test262Dir;
+// where to load includes from (usually a subdirectory of test262dir)
+let includesDir = argv.includesDir;
+
+// initialize reporter by attempting to load lib/reporters/${reporter}
+// defaults to 'simple'
 let reporter;
 if (fs.existsSync(Path.join(__dirname, '../lib/reporters', argv.reporter + '.js'))) {
   reporter = require('../lib/reporters/' + argv.reporter + '.js');
@@ -23,8 +30,13 @@ if (fs.existsSync(Path.join(__dirname, '../lib/reporters', argv.reporter + '.js'
   process.exit(1);
 }
 
-let includesDir = argv.includesDir;
-let test262Dir = argv.test262Dir;
+// load preload contents
+let preludeContents;
+if (argv.prelude) {
+  preludeContents = fs.readFileSync(argv.prelude, 'utf8');
+} else {
+  preludeContents = '';
+}
 
 // Select hostType and hostPath. hostType defaults to 'node'.
 // If using default hostType, hostPath defaults to the current node executable location.
@@ -76,5 +88,6 @@ function pathToTestFile(path) {
 }
 
 function compileFile(contents) {
+  contents = preludeContents + contents;
   return compile(contents, { test262Dir: test262Dir, includesDir: includesDir });
-}
+}
\ No newline at end of file
diff --git a/lib/cli.js b/lib/cli.js
index ff73f67..661278c 100644
--- a/lib/cli.js
+++ b/lib/cli.js
@@ -8,6 +8,8 @@ const yargv = yargs
   .describe('test262Dir', 'test262 root directory')
   .describe('includesDir', 'directory where helper files are found')
   .describe('threads', 'number of threads to use')
+  .describe('prelude', 'content to include above each test')
+  .nargs('prelude', 1)
   .nargs('threads', 1)
   .default('threads', 1)
   .alias('threads', 't')