Many methods of contraception involve the use of drugs that affect the secretion of hormones essential for reproduction. Oestrogens and progestins have been used for contraction in women as inhibitors of gonadotrophin secretion and ovulation. Similarly, androgens must be used in methods of fertility control for men that block gonadotrophin secretion. Androgen supplementation currently involves large, frequent doses of testosterone esters that are associated with wide fluctuations of plasma testosterone levels. Hence, there is a need for an androgen preparation that provides appropriate, continuous replacement doses over long periods. To achieve this goal, 7 alpha-methyl-19-nortestosterone (MENT), a synthetic androgen that is considerably more potent than testosterone, is suitable. As a consequence, it is feasible to administer this androgen as a substitute for testosterone for 1 year by subdermal implants. Another important feature of MENT is that it does not undergo 5 alpha- reduction in prostate as does testosterone. As a consequence, a dose of MENT sufficient to maintain normal muscle mass and gonadotrophin secretion will not hyperstimulate the prostate because its action in this organ is not amplified as is that of testosterone. Thus, MENT can be administered to men with the assurance that it will be less prone to cause diseases of the prostate than testosterone. CONCLUSIONS (i) MENT is the first androgen that has a health benefit compared to testosterone; (ii) MENT will be promoted as one component of a two-implant system for male contraception, the other component being an implant that will release an LHRH analogue; (iii) MENT has potential uses in patients with a variety of disorders, including hypogonadism, prostatic hyperplasia and muscle wasting.