Some tangible progress has been made recently in electronic Proximity Warning Devices (PWD) for specialized applications. This paper discusses recent Bendix Avionics efforts in this field for U. S. Army Aviation helicopters. Such devices have been demonstrated and are feasible in certain environments. The technical limitations of an Interrogator/Transponder (I/T) range/altitude (PWD) are covered. Current status of other radio frequency and infrared PWD's and the compatibility of these devices with the Air Transport Association's Collision Avoidance System is discussed.