The fungus, Cephalosporium aphidicola, has been shown to hydroxylate progesterone predominantly at the 6 beta- and 11 alpha-positions. Minor metabolites include testosterone acetate, the 20(R)-alcohol and 12 beta, 17 alpha-dihydroxy-progesterone. The sequence involves hydroxylation at 11 alpha and then 6 beta. The hydroxylations of 11 alpha- and 17 alpha-hydroxyprogesterone and of 9 beta, 10 alpha-retroprogesterone have also been examined in the light of these results.