NOL's Hypersonic Tunnel No. 4 is a continuous blow-down hypersonic tunnel designed for research and development testing of models, instrumentation, and wind tunnel components. It can operate at Mach numbers from 5 to 10 with supply pressures up to 52 atmospheres and supply temperatures up to 1700 R. This report summarizes the pertinent aerodynamic design criteria and operating experience compiled during its first eleven years of operation. Included are descriptions of the major components and their performance along with the flight simulation capability of the facility and a bibliography of previously published reports. (Author).