Metabolism of the anabolic steroidal hormone methandrostenolone in Wistar rats was studied by high performance liquid chromatography (HPLC) and redioisotope techniques. The conditions for isolation of methandrostenolone metabolites by HPLC were developed. Reduction of the double bonds was shown to be an early stage in methandrostenolone biotransformation. The main portion of the metabolites was excreted with urine as glucuronide conjugates. No sulfoesters were found.