Alamofire.request(.POST, "http://www.webapi.com?path=Login", parameters: ["username": "myname", "password": "mypass"]).responseJSON { response in
// do something with returned data ...
}

let request = NSMutableURLRequest(URL: NSURL(string:"http://www.webapi.com?path=Login")!)

let bodyData = "username=myname&password=mypass"
request.HTTPBody = bodyData.dataUsingEncoding(NSUTF8StringEncoding)
request.HTTPMethod = "POST"

let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())

    session.dataTaskWithRequest(request) { (data, response, error) -> Void in

    // do something with returned data...

    }.resume()