Abstract Removal of the C-10 methyl group of testosterone, its acetate, methyltestosterone, and Δ 4-androstene-3,17-dione enhances local androgenic activity on the chick comb. Introduction of a 7α-methyl group generally decreases local activity but modestly increases potency upon systemic administration to rodents. If the 7α-methylation is done to the 19-nor steroids, protection is afforded to the locally active 19-nor configuration, permitting the delivery of the 19-nor steroid to the end organ even after systemic administration, with resultant substantial increases (averaging 10-fold) in androgenicity. The increase is greatest in 7α,17α-dimethyl-19-nortestosterone and least in 7α-methyl-19-nor-androst-4-ene-3,17-dione. The thesis is advanced that the 19-nor androgens may well be the active androgens at the end organ, that they in turn give rise to the estrogens, and that testosterone merely serves as a precursor of the active 19-nor steroids.