The tissue distribution, metabolism, and elimination of 14C-octachlorostyrene (OCS) were studied in the rat. OCS was absorbed in the gastrointestinal tract after oral administration and distributed in all tissues examined. The highest concentrations were found in fat followed by adrenal glands, skin, and lungs. Decay of radioactivity in the tissues followed first-order kinetics. Approximately 8% of an iv dose was excreted in feces during 7 days after administration, while negligible amounts were found in the urine. More than 90% of the radioactivity in feces was due to the unchanged compound, while pentachlorophenyldichloroacetic acid and heptachlorostyrene in equal proportions accounted for the remaining 10%. A small amount (1%) of the dose was detected in the expired air as carbon dioxide.