Depot medroxyprogesterone acetate (DMPA) was tested for suppressive effects on spermatogenesis in 29 men. DMPA was administered as a monthly injection of 100 or 150 mg; in addition, testosterone was given either in subdermal sustained release implants of testosterone propionate (TP), or as a monthly injection of 100 or 250 mg testosterone enanthate (TE). Sperm production was reduced in 28/29 subjects. In most instances, production was severely inhibited, as indicated either by sperm counts below 1 million/ml, or by testicular biopsy showing spermatogenic arrest. No changes were reported or observed in the size, consistency, or sensitivity of breasts, testicles or prostate. Some subjects reported slight initial decreases in libido, but returned to normal after the first few weeks of treatment. Metabolic parameters were measured in some subjects, and showed no significant changes. Transient weight gain occurred in a few subjects.