Instrumentation for studying the propagation of near-millimeter waves has been designed and is currently being implemented at a 1 mile long test site in Sandusky, Ohio. An optically pumped near-millimeter (NMM) wave laser, used as a source of radiation for frequencies near 300 GHz, is located at one end of this site. The laser beam spot size arriving at the other end of the propagation path is controlled by a two-lens optical system placed at the laser's output. The receiver system consists of a parabolic reflector, a focal plane scanning system, and a fast-response liquid-helium-cooled InSb detector, all of which is controlled by a 68000-based microcomputer. Measurement of the characteristics of the received beam is based upon a quasi-optical method. The temperature/humidity atmospheric structure parameters and hydrometeor characteristics along the path are obtained simultaneously with the propagation measurements. These two measurements are then correlated to provide a meteorologically well-verified propagation model for near-millimeter wavelengths.