Ion mobility spectrometry (IMS) was first introduced in the late 1960s as an instrumental technique for detecting organic compounds at trace concentrations in air. Despite certain at tractive features of IMS in environmental mon itoring and laboratory studies, the growth of IMS from 1970 to 1980 exhibited some disappointing trends as suggested in Figure 1. Interest in IMS declined generally after 1976 by what may be ascribed to a broad disenchantment from unmet expectations and misunderstanding of response characteristics. A new cycle of interest in IMS began 1980 resulting in advances in all aspects of IMS. Additionally, small rugged IMS units suited for operation in hostile environments became available in fulfillment of the purposes originally suggested for IMS. This has occurred through unpublicized developmental programs within military establishments of the U.S. and the U.K.