Four pools were observed in Banners Corner Cave, Russell County, Virginia, over a 28 month period from November 1961 to February 1964. Three of these pools were visibly polluted with sewage which had seeped into the cave from septic tanks located on the hill above. All four of these pools, at one time or another during the study, contained large populations of planarians, Phagocata subterranea Hyman and isopods, Asellus recurvatus Steeves. Physicochemical and microbiological analyses of the pool waters indicated that oxygen tension is a low as 2.8 mg./l. in one pool and that coliforms and other forms of bacteria (probably saprophytic) are abundant in the contaminated waters of the cave. Microscopic examination of the pool waters revealed a rich and varied microfauna, especially protozoans and rotifers. In addition, the polluted pools contained large amounts of colloidal materials which are believed to be rich in organic content. The influx and accumulation of sewage rich in organic matter is believed to be the basic trophic input in the contaminated pools. It is suggested that this material serves as an important food source for saprophytic bacteria as well as for much of the aquatic fauna, including both micro- and macroforms. Precise trophic relationships between the larger aquatic organisms have not been worked out but several significant feeding responses have been observed.