Increased air traffic coupled with the proliferation of sophisticated avionics can be expected to stimulate increased demand for air traffic control (ATC) services over the next few decades. New challenges for the design of communication, surveillance, and navigation subsystems is an anticipated consequence. Since it is unlikely that significantly larger frequency bands will become available, it will be necessary to exploit more efficient multiple-access techniques. The design of a multiple-access technique for a particular application will depend on a broad range of system issues. A predetermined procedure based on general characteristics of the various techniques will have but limited value. An example of an ATC satellite surveillance system is used to illustrate some of the broad ranging systems issues that can be expected to influence the selection of the multiple access technique.