In order to determine the effect on biological activity (in the rat) brought about by the conversion of the α, β-unsaturated carbonyl group to an enol ether, a variety of methyltestosterone ethers were assayed, orally and parenterally, with respect to androgenic and myogenic activity. The enol ethers were found, rather surprisingly, more active than the parent ketone when given by mouth, but less active when injected. The influence upon activity by the character of alcoholic chain is discussed.