The US DOE is engaged in broad, multi-disciplinary research to address the environmental concerns associated with in situ oil shale processing. A significant portion of this research effort has been directed at the characterization, transport, geohydrological interactions, biological effects, containment, treatment, and utilization of waters, heavily laden with organic and inorganic solutes, which are produced during the in situ process. This paper discusses the sources and quantities of produced retort waters and provides a summary overview of water related environmental research, conducted principally through the Laramie Energy Research Center since 1974, in conjunction with simulated and field in situ processing experiments.