The test article, hexabromocyclododecane (HBCD), in the vehicle, corn oil, was administered orally (gavage) to three groups of Crl:CD(SD)BR rats for 28 consecutive days. Dosage levels of 125, 350 and 1000 mg/kg/day were administered at a dose volume of 5 ml/kg. The treated groups consisted of 6 rats/sex in the 125 and 350 mg/kg/day groups and 12 rats/sex in the 1000 mg/kg/day group. A concurrent control group comprised of 12 rats/sex received the vehicle on a comparable regimen. Peameters that were evaluated included survival, clinical condition, body weights, food consumption, functional observational battery performance, motor activity, hematology and serum chemistry. At the conclusion of the four-week dosing period, 6 rats/sex/group were enthanized and necropsied. The remaining 6 rats/sex in the control and 1000 mg/kg/day groups were euthanized and necropsied following a two-week recovery period. Selected organs were weighed and/or preserved and selected tissues were examined microscopically for each animal. summer of 1981 to conduct an independent investigation to determine the effects of exposure to chromium compounds on human health and the environment. Battelle's study included a critical review of selected publications relating to chromina toxicity, a comprehensive survey of all 30 refractory plant locations in the United States, site visits to a representa- tive group of manufacturing plants, and an analytical assessment to determine if trivalent chromium compounds used in manufacturing refractories were con- verted to hexavalent materials during the manufacturing process.