diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..713bd2f
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,122 @@
+
+import { OutgoingMessage } from "http";
+
+export default Router;
+
+type HttpMethods = 
+  'get' |
+  'post' |
+  'put' |
+  'head' |
+  'delete' |
+  'options' |
+  'trace' |
+  'copy' |
+  'lock' |
+  'mkcol' |
+  'move' |
+  'purge' |
+  'propfind' |
+  'proppatch' |
+  'unlock' |
+  'report' |
+  'mkactivity' |
+  'checkout' |
+  'merge' |
+  'm-search' |
+  'notify' |
+  'subscribe' |
+  'unsubscribe' |
+  'patch' |
+  'search' |
+  'connect'
+
+export interface RouterOptions {
+  strict?: boolean;
+  caseSensitive?: boolean;
+  mergeParams?: boolean;
+}
+
+export interface IncomingRequest {
+  url?: string;
+  method?: string;
+  originalUrl?: string;
+  params?: Record<string, string>;
+}
+
+interface BaseRoutedRequest extends IncomingRequest {
+  baseUrl: string;
+  next?: NextFunction;
+  route?: IRoute;
+}
+
+export type RoutedRequest = BaseRoutedRequest & {
+  [key: string]: any;
+}
+
+export interface NextFunction {
+  (err?: any): void;
+}
+
+type IRoute = Record<HttpMethods, IRouterHandler<IRoute>> & {
+  path: string;
+  all: IRouterHandler<IRoute>;
+}
+
+type RequestParamHandler = (
+  req: IncomingRequest,
+  res: OutgoingMessage,
+  next: NextFunction,
+  value: string,
+  name: string
+) => void;
+
+export interface RouteHandler {
+  (req: RoutedRequest, res: OutgoingMessage, next: NextFunction): void;
+}
+
+export interface RequestHandler {
+  (req: IncomingRequest, res: OutgoingMessage, next: NextFunction): void;
+}
+
+type ErrorRequestHandler = (
+  err: any,
+  req: IncomingRequest,
+  res: OutgoingMessage,
+  next: NextFunction
+) => void;
+
+type PathParams = string | RegExp | Array<string | RegExp>;
+
+type RequestHandlerParams =
+  | RouteHandler
+  | ErrorRequestHandler
+  | Array<RouteHandler | ErrorRequestHandler>;
+
+interface IRouterMatcher<T> {
+  (path: PathParams, ...handlers: RouteHandler[]): T;
+  (path: PathParams, ...handlers: RequestHandlerParams[]): T;
+}
+
+interface IRouterHandler<T> {
+  (...handlers: RouteHandler[]): T;
+  (...handlers: RequestHandlerParams[]): T;
+}
+
+type IRouter = Record<HttpMethods, IRouterMatcher<IRouter>> & {
+  param(name: string, handler: RequestParamHandler): IRouter;
+  param(
+    callback: (name: string, matcher: RegExp) => RequestParamHandler
+  ): IRouter;
+  all: IRouterMatcher<IRouter>;
+  use: IRouterHandler<IRouter> & IRouterMatcher<IRouter>;
+  handle: RequestHandler;
+  route(prefix: PathParams): IRoute;
+}
+
+interface RouterConstructor {
+  new (options?: RouterOptions): IRouter & RequestHandler;
+  (options?: RouterOptions): IRouter & RequestHandler;
+}
+
+declare var Router: RouterConstructor;
diff --git a/test/types.ts b/test/types.ts
new file mode 100644
index 0000000..fc85c83
--- /dev/null
+++ b/test/types.ts
@@ -0,0 +1,89 @@
+import { createServer, OutgoingMessage } from 'http';
+import Router, {
+  RouterOptions,
+  RouteHandler,
+  NextFunction,
+  RoutedRequest,
+  IncomingRequest
+} from '..';
+
+const options: RouterOptions = {
+  strict: false,
+  caseSensitive: false,
+  mergeParams: false
+};
+
+// new constructor
+new Router().all('/', (req, res, next) => {})
+// direct call
+Router().all('/', (req, res, next) => {})
+
+const router = new Router(options);
+const routerHandler: RouteHandler = (req, res, next) => {
+    res.setHeader('Content-Type', 'plain/text');
+    res.write('Hello')
+    res.end('world')
+};
+
+// test verb methods
+router.get('/', routerHandler);
+router.post('/', routerHandler);
+router.delete('/', routerHandler);
+router.patch('/', routerHandler);
+router.options('/', routerHandler);
+router.head('/', routerHandler);
+router.bind('/', routerHandler);
+router.connect('/', routerHandler);
+router.trace('/', routerHandler);
+router['m-search']('/', routerHandler);
+
+
+// param
+router.param('user_id', (req, res, next, id) => {
+  type TReq = Expect<Equal<typeof req, IncomingRequest>>
+  type TRes = Expect<Equal<typeof res, OutgoingMessage>>
+  type TNext = Expect<Equal<typeof next, NextFunction>>
+  type P1 = Expect<Equal<typeof id, string>>
+});
+
+// middleware
+router.use((req, res, next) => {
+    type TReq = Expect<Equal<typeof req, RoutedRequest>>
+    type TRes = Expect<Equal<typeof res, OutgoingMessage>>
+    type TNext = Expect<Equal<typeof next, NextFunction>>
+    next();
+});
+
+// RoutedRequest is extended with properties without type errors
+router.use((req, res, next) => {
+  req.extendable = 'extendable'
+  next();
+});
+
+router.route('/')
+.all((req, res, next) => {
+    type TReq = Expect<Equal<typeof req, RoutedRequest>>
+    type TRes = Expect<Equal<typeof res, OutgoingMessage>>
+    type TNext = Expect<Equal<typeof next, NextFunction>>
+    next();
+})
+.get((req, res, next) => {
+    type TReq = Expect<Equal<typeof req, RoutedRequest>>
+    type TRes = Expect<Equal<typeof res, OutgoingMessage>>
+    type TNext = Expect<Equal<typeof next, NextFunction>>
+});
+
+
+// valid for router from createServer
+createServer(function(req, res) {
+  router(req, res, (err) => {})
+  router.handle(req, res, (err) => {})
+})
+
+
+// Type test helper methods
+type Compute<T> = T extends (...args: any[]) => any ? T : { [K in keyof T]: Compute<T[K]> }
+
+type Equal<X, Y> = (<T>() => T extends Compute<X> ? 1 : 2) extends <T>() => T extends Compute<Y> ? 1 : 2 ? true : false
+
+type Expect<T extends true> = T extends true ? true : never