diff --git a/dist/main/lang/modules/building.js b/dist/main/lang/modules/building.js
index 9b8b0d332..b87af35b1 100644
--- a/dist/main/lang/modules/building.js
+++ b/dist/main/lang/modules/building.js
@@ -1,6 +1,8 @@
 var mkdirp = require('mkdirp');
 var path = require('path');
 var fs = require('fs');
+var fsUtil_1 = require("../../utils/fsUtil");
+var babel;
 exports.Not_In_Context = "/* NotInContext */";
 function diagnosticToTSError(diagnostic) {
     var filePath = diagnostic.file.fileName;
@@ -29,10 +31,20 @@ function emitFile(proj, filePath) {
         var startPosition = diagnostic.file.getLineAndCharacterOfPosition(diagnostic.start);
         errors.push(diagnosticToTSError(diagnostic));
     });
-    output.outputFiles.forEach(function (o) {
-        mkdirp.sync(path.dirname(o.name));
-        fs.writeFileSync(o.name, o.text, "utf8");
-    });
+    {
+        var sourceMapContents = {};
+        output.outputFiles.forEach(function (o) {
+            mkdirp.sync(path.dirname(o.name));
+            var additionalEmits = runExternalTranspiler(o, proj, sourceMapContents);
+            if (!sourceMapContents[o.name]) {
+                fs.writeFileSync(o.name, o.text, "utf8");
+            }
+            additionalEmits.forEach(function (a) {
+                mkdirp.sync(path.dirname(a.name));
+                fs.writeFileSync(a.name, a.text, "utf8");
+            });
+        });
+    }
     var outputFiles = output.outputFiles.map(function (o) { return o.name; });
     if (path.extname(filePath) == '.d.ts') {
         outputFiles.push(filePath);
@@ -61,3 +73,71 @@ function getRawOutput(proj, filePath) {
     return output;
 }
 exports.getRawOutput = getRawOutput;
+function runExternalTranspiler(outputFile, project, sourceMapContents) {
+    if (!isJSFile(outputFile.name) && !isJSSourceMapFile(outputFile.name)) {
+        return [];
+    }
+    var settings = project.projectFile.project;
+    var externalTranspiler = settings.externalTranspiler;
+    if (!externalTranspiler) {
+        return [];
+    }
+    if (isJSSourceMapFile(outputFile.name)) {
+        var sourceMapPayload = JSON.parse(outputFile.text);
+        var jsFileName = fsUtil_1.consistentPath(path.resolve(path.dirname(outputFile.name), sourceMapPayload.file));
+        sourceMapContents[outputFile.name] = { jsFileName: jsFileName, sourceMapPayload: sourceMapPayload };
+        return [];
+    }
+    if (externalTranspiler.toLocaleLowerCase() === "babel") {
+        babel = require("babel");
+        var babelOptions = {};
+        var sourceMapFileName = getJSMapNameForJSFile(outputFile.name);
+        if (sourceMapContents[sourceMapFileName]) {
+            babelOptions.inputSourceMap = sourceMapContents[sourceMapFileName].sourceMapPayload;
+        }
+        if (settings.compilerOptions.sourceMap) {
+            babelOptions.sourceMaps = true;
+        }
+        if (settings.compilerOptions.inlineSourceMap) {
+            babelOptions.sourceMaps = "inline";
+        }
+        if (!settings.compilerOptions.removeComments) {
+            babelOptions.comments = true;
+        }
+        var babelResult = babel.transform(outputFile.text, babelOptions);
+        outputFile.text = babelResult.code;
+        if (babelResult.map && settings.compilerOptions.sourceMap) {
+            var additionalEmit = {
+                name: sourceMapFileName,
+                text: JSON.stringify(babelResult.map),
+                writeByteOrderMark: settings.compilerOptions.emitBOM
+            };
+            if (additionalEmit.name === "") {
+                console.warn("The TypeScript language service did not yet provide a .js.map name for file " + outputFile.name);
+                return [];
+            }
+            return [additionalEmit];
+        }
+        return [];
+    }
+    function getJSMapNameForJSFile(jsFileName) {
+        for (var jsMapName in sourceMapContents) {
+            if (sourceMapContents.hasOwnProperty(jsMapName)) {
+                if (sourceMapContents[jsMapName].jsFileName === jsFileName) {
+                    return jsMapName;
+                }
+            }
+        }
+        return "";
+    }
+}
+function isJSFile(fileName) {
+    return (path.extname(fileName).toLocaleLowerCase() === ".js");
+}
+function isJSSourceMapFile(fileName) {
+    var lastExt = path.extname(fileName);
+    if (lastExt === ".map") {
+        return isJSFile(fileName.substr(0, fileName.length - 4));
+    }
+    return false;
+}
diff --git a/dist/main/tsconfig/tsconfig.js b/dist/main/tsconfig/tsconfig.js
index 992b6bba9..d9638d8b9 100644
--- a/dist/main/tsconfig/tsconfig.js
+++ b/dist/main/tsconfig/tsconfig.js
@@ -240,7 +240,8 @@ function getProjectSync(pathOrSrcFile) {
         formatCodeOptions: formatting.makeFormatCodeOptions(projectSpec.formatCodeOptions),
         compileOnSave: projectSpec.compileOnSave == undefined ? true : projectSpec.compileOnSave,
         package: pkg,
-        typings: []
+        typings: [],
+        externalTranspiler: projectSpec.externalTranspiler == undefined ? undefined : projectSpec.externalTranspiler
     };
     var validationResult = validator.validate(projectSpec.compilerOptions);
     if (validationResult.errorMessage) {
diff --git a/docs/faq.md b/docs/faq.md
index 476854fe6..58fbe29e2 100644
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -14,6 +14,22 @@ If it conforms the latest TypeScript services API then yes! Just set the path to
 
 However, please note that the [version](https://github.com/TypeStrong/atom-typescript/blob/master/docs/tsconfig.md#version) in `tsconfig.json` does not indicate the compiler atom is using.  That's strictly an aide-mémoire - it's to remind you which version of the TypeScript this project is intended to work with.
 
+## Can I use an alternate transpiler?
+Atom-typescript supports using Babel as an alternate ES5 transpiler in coordination with the TypeScript language service.  This may be useful if TypeScript does not yet support transpiling a certain feature correctly (for example [scope per for loop iteration with let](https://github.com/Microsoft/TypeScript/issues/3915)).
+
+To enable using Babel as the transpiler, make these changes to your `tsconfig.json` file:
+
+**1:** Add this key in the root:
+
+```js
+{
+ "externalTranspiler": "babel"
+}
+```
+**2:** Set the `target` compiler option to `"es6"`.  This is not *technically* required, but if you don't do this, you'll just be transpiling an already-transpiled file.
+
+Note that atom-typescript's Babel integraion works with in concert with the `removeComments`, `sourceMap`, and `inlineSourceMap` compiler options settings in `tsconfig.json`, so those items should just work as expected.  Any source maps should be doubly-mapped back to the original TypeScript.
+
 ## I prefer single (or double) quotes
 You can set that in the package settings https://atom.io/docs/latest/using-atom-atom-packages#package-settings
 
diff --git a/lib/main/atom/atomUtils.ts b/lib/main/atom/atomUtils.ts
index bf276cb42..a21ae161c 100644
--- a/lib/main/atom/atomUtils.ts
+++ b/lib/main/atom/atomUtils.ts
@@ -19,7 +19,7 @@ export function getEditorPositionForBufferPosition(editor: AtomCore.IEditor, buf
     return buffer.characterIndexForPosition(bufferPos);
 }
 
-export function isAllowedExtension(ext) {
+export function isAllowedExtension(ext: string) {
     return (ext == '.ts' || ext == '.tst' || ext == '.tsx');
 }
 
diff --git a/lib/main/lang/modules/building.ts b/lib/main/lang/modules/building.ts
index 4d66b065d..ccc9868c2 100644
--- a/lib/main/lang/modules/building.ts
+++ b/lib/main/lang/modules/building.ts
@@ -6,6 +6,7 @@ import {pathIsRelative, makeRelativePath} from "../../tsconfig/tsconfig";
 import {consistentPath} from "../../utils/fsUtil";
 import {createMap} from "../utils";
 
+let babel: any;
 export const Not_In_Context = "/* NotInContext */";
 
 export function diagnosticToTSError(diagnostic: ts.Diagnostic): TSError {
@@ -40,10 +41,23 @@ export function emitFile(proj: project.Project, filePath: string): EmitOutput {
         errors.push(diagnosticToTSError(diagnostic));
     });
 
-    output.outputFiles.forEach(o => {
-        mkdirp.sync(path.dirname(o.name));
-        fs.writeFileSync(o.name, o.text, "utf8");
-    });
+    {
+      let sourceMapContents: {[index:string]: any} = {};
+      output.outputFiles.forEach(o => {
+          mkdirp.sync(path.dirname(o.name));
+          let additionalEmits = runExternalTranspiler(o, proj, sourceMapContents);
+
+          if (!sourceMapContents[o.name]) {
+              // .js.map files will be written as an "additional emit" later.
+              fs.writeFileSync(o.name, o.text, "utf8");
+          }
+
+          additionalEmits.forEach(a => {
+              mkdirp.sync(path.dirname(a.name));
+              fs.writeFileSync(a.name, a.text, "utf8");
+            })
+      });
+    }
 
     var outputFiles = output.outputFiles.map((o) => o.name);
     if (path.extname(filePath) == '.d.ts') {
@@ -71,3 +85,90 @@ export function getRawOutput(proj: project.Project, filePath: string): ts.EmitOu
     }
     return output;
 }
+
+function runExternalTranspiler(outputFile: ts.OutputFile, project: project.Project, sourceMapContents: {[index:string]: any}) : ts.OutputFile[] {
+  if (!isJSFile(outputFile.name) && !isJSSourceMapFile(outputFile.name)) {
+    return [];
+  }
+
+  let settings = project.projectFile.project;
+  let externalTranspiler = settings.externalTranspiler;
+  if (!externalTranspiler) {
+    return [];
+  }
+
+  if (isJSSourceMapFile(outputFile.name)) {
+    let sourceMapPayload = JSON.parse(outputFile.text);
+    let jsFileName = consistentPath(path.resolve(path.dirname(outputFile.name), sourceMapPayload.file));
+    sourceMapContents[outputFile.name] = {jsFileName: jsFileName, sourceMapPayload};
+    return [];
+  }
+
+  if (externalTranspiler.toLocaleLowerCase() === "babel") {
+    babel = require("babel");
+
+    let babelOptions : any = {};
+
+    let sourceMapFileName = getJSMapNameForJSFile(outputFile.name);
+
+    if (sourceMapContents[sourceMapFileName]) {
+      babelOptions.inputSourceMap = sourceMapContents[sourceMapFileName].sourceMapPayload;
+    }
+    if (settings.compilerOptions.sourceMap) {
+      babelOptions.sourceMaps = true;
+    }
+    if (settings.compilerOptions.inlineSourceMap) {
+      babelOptions.sourceMaps = "inline";
+    }
+    if (!settings.compilerOptions.removeComments) {
+      babelOptions.comments = true;
+    }
+
+    let babelResult = babel.transform(outputFile.text, babelOptions);
+    outputFile.text = babelResult.code;
+
+    if (babelResult.map && settings.compilerOptions.sourceMap) {
+      let additionalEmit : ts.OutputFile = {
+        name: sourceMapFileName,
+        text : JSON.stringify(babelResult.map),
+        writeByteOrderMark: settings.compilerOptions.emitBOM
+      };
+
+      if (additionalEmit.name === "") {
+        // can't emit a blank file name - this should only be reached if the TypeScript
+        // language service returns the .js file before the .js.map file.
+        console.warn(`The TypeScript language service did not yet provide a .js.map name for file ${outputFile.name}`);
+        return [];
+      }
+
+      return [additionalEmit];
+    }
+
+    return [];
+  }
+
+  function getJSMapNameForJSFile(jsFileName: string) {
+    for (let jsMapName in sourceMapContents) {
+      if (sourceMapContents.hasOwnProperty(jsMapName)) {
+        if (sourceMapContents[jsMapName].jsFileName === jsFileName) {
+          return jsMapName;
+        }
+      }
+    }
+    return "";
+  }
+}
+
+
+
+function isJSFile(fileName: string) {
+  return (path.extname(fileName).toLocaleLowerCase() === ".js");
+}
+
+function isJSSourceMapFile(fileName: string) {
+  let lastExt = path.extname(fileName);
+  if (lastExt === ".map") {
+    return isJSFile(fileName.substr(0,fileName.length - 4));
+  }
+  return false;
+}
diff --git a/lib/main/tsconfig/tsconfig.ts b/lib/main/tsconfig/tsconfig.ts
index bbac22597..22d6bc490 100644
--- a/lib/main/tsconfig/tsconfig.ts
+++ b/lib/main/tsconfig/tsconfig.ts
@@ -102,6 +102,7 @@ interface TypeScriptProjectRawSpecification {
     filesGlob?: string[];                               // optional: An array of 'glob / minimatch / RegExp' patterns to specify source files
     formatCodeOptions?: formatting.FormatCodeOptions;   // optional: formatting options
     compileOnSave?: boolean;                            // optional: compile on save. Ignored to build tools. Used by IDEs
+    externalTranspiler?: string;
 }
 
 interface UsefulFromPackageJson {
@@ -123,6 +124,7 @@ export interface TypeScriptProjectSpecification {
     formatCodeOptions: ts.FormatCodeOptions;
     compileOnSave: boolean;
     package?: UsefulFromPackageJson;
+    externalTranspiler?: string;
 }
 
 ///////// FOR USE WITH THE API /////////////
@@ -404,7 +406,8 @@ export function getProjectSync(pathOrSrcFile: string): TypeScriptProjectFileDeta
         formatCodeOptions: formatting.makeFormatCodeOptions(projectSpec.formatCodeOptions),
         compileOnSave: projectSpec.compileOnSave == undefined ? true : projectSpec.compileOnSave,
         package: pkg,
-        typings: []
+        typings: [],
+        externalTranspiler: projectSpec.externalTranspiler == undefined ? undefined : projectSpec.externalTranspiler
     };
 
     // Validate the raw compiler options before converting them to TS compiler options
diff --git a/package.json b/package.json
index 553c80bdf..105669ab4 100644
--- a/package.json
+++ b/package.json
@@ -42,6 +42,7 @@
   "dependencies": {
     "atom-package-dependencies": "https://github.com/basarat/atom-package-dependencies/archive/cb1.tar.gz",
     "atom-space-pen-views": "^2.0.4",
+    "babel": "^5.6.23",
     "basarat-text-buffer": "6.0.0",
     "d3": "^3.5.5",
     "emissary": "^1.3.3",