Because of the limitations of pump-and-treat technology, attention is now focused on the feasibility of surfactant use to increase its efficiency. Surfactants have been studied for use in soil washing and enhanced oil recovery. Although similarities exist between the applications, there are significant differences in the objectives of the technologies and the limitations placed on surfactant use. In this article we review environmental studies concerned with the fate and transport of surface-active compounds in the subsurface environment and discuss key issues related to their successful use for in situ aquifer remediation, particularly with respect to nonaqueous-phase liquids. (Copyright (c) 1992 American Chemical Society.)