The metabolic fate and distribution of the anti-androgenic agent, 17 alpha-acetoxy-6-chloropregna-4, 6-diene-3, 20-dione (chlormadinone acetate, CMA), was investigated using guinea-pigs and rats. In order to elucidate the metabolic outcome, chlormadinone acetate was labelled with 3H at position C-1 and with deuterium at methyl moiety of the 17alpha-acetate.