To obtain a medicine effective in prevention, treatment, etc., of male impotentia generandi related to insufficient fertility of a sperm by using a 3a-hydroxy-5α-androst-16-ene (ester) as an active ingredient.

A 3α-hydroxy-5α-androst-16-ene represented by the formula and its ester are used as an active ingredient and blended with an adjuvant usually used in a pharmaceutical composition, e.g. talc, gum arabic, lactose, starch, magnesium stearate, cocoa butter, an aqueous or a nonaqueous vehicle, an animal or a vegetable fatty substance, a paraffinic derivative, glycols, various wetting or dispersing or emulsifying agents or preservatives and formulating a pharmaceutical preparation. The resultant medicine is useful for prevention and/or treatment, etc., of certain kinds of forms of male impotentia generandi related to insufficient fertility of a sperm.