The southern San Joaquin Valley has been the site of extensive oil production from the late 1800s to the present. Within the past decade, the disposal of waste fluids associated with exploration, production, storage, and transportation of petroleum has become a concern with regard to ground-water quality. Portions of the San Joaquin Valley, particularly the Buena Vista Valley area, contain ground water with naturally occurring high salinity and total dissolved solids (TDS). These waters have been extracted during oil production, and used for water flood and steam injection operations, further elevating the concentration of salts and other compounds. The recent passage of several environmental laws in California has required disposal of these concentrated fluids at licensed disposal sites. These sites require specific siting criteria, engineering and hydrogeologic evaluation, fluid containment, and long-term unsaturated zone and ground-water monitoring. Disposal facilities operating prior to the implementation of the new criteria may also require hydrogeologic characterization in compliance with state regulations. This paper will provide an overview of past practices, natural hydrogeologic conditions, current regulatory context, and water quality issues at several oil field disposal facilities in the southern San Joaquin Valley.