The mm-wave (10-110 GHz) frequency band contains the fundamental rotational resonance frequencies of many molecular gases composed of carbon, nitrogen, oxygen and sulfur. The high specificity of the rotational spectra to organic molecules affords mm-wave spectroscopy having potential use in remotely sensing atmospheric pollutants and the detection of airborne chemicals is gaining importance for arms control treaty verification, intelligence collection and environmental monitoring. This paper considers RF receiver systems for remote chemical detection measurements based on mm-wave spectral line emissions. It discusses the design, performance and operation of specific receiving systems for detecting the presence of ammonia in laboratory based transmit-and-receive experiments.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.