The ability to send headers for AMF remoting calls is supported in the lower level flex classes but not exposed in the RemoteObject class. GEMVC now includes (in the trunk of SVN) its own extension of the RemoteObject and Operation classes that allow you to set these headers. All you have to do is set the headers global on your AMF Service or set them on the MVCAMFCommandInfo class when you call your remote service. One caveat though: These headers are not placed in the HTTP headers, they are actually encoded in the AMF packet (why?) so your backend AMF gateway must be able to retrieve them. With Coldfusion 8 I have not been able to access these headers but I have included them anyway in case other configurations can.