The need for an effective airborne collision system has already been established. In response the FAA has developed a three-member family of Traffic Alert and Collision Avoidance Systems for use by the full spectrum of aircraft. The performance of the systems depends upon the presentation of the TCAS information to the crew in such a way that it can be used effectively in an operational environment. These presentations need to be easy to comprehend and representative of real-world relationships--in a word, intuitive.This paper discusses the need for intuitiveness in the TCAS display. It reviews fundamental principles of perception, critiques the existing TCAS II display, and urges the application of innovative techniques in the design of future systems.