Open and double-blind therapeutic studies were carried out on the effects of tamoxifen in oligozoospermia. The examinations involved 74 patients. The first group (n = 20) received tamoxifen 20 mg/day; the second group (n = 54) got tamoxifen or placebo for 3 months. In the open study, tamoxifen treatment led to significant increases in the spermatozoa concentration and the total sperm count, but this could not be confirmed with the double-blind set-up.