Laboratory biobarriers were evaluated for their ability to remove selenite from flowing groundwater. Microbial activity in aquifers is usually limited by substrate availability, and biobarriers stimulate microbial activity by providing a substrate, for these studies soybean oil was used. Water containing, 10 mg L-1 selenite-Se was pumped through the biobarriers for 74 days and the amount present in the effluent monitored. The amounts remained high for the first 2 weeks of the study but then declined. From day 28 until the end of the study the amount of selenite-Se in the column effluents averaged 0.20 +/- 0.04 mg L-1. a decrease of approximately 98%. At the end of the Study about half of the selenite-Se applied to the columns was recovered as immobilized selenium trapped by the biobarrier. This study Suggests that biobarriers containing vegetable oil might be used as a process for removing selenite from contaminated groundwater.