This study of the effects of long-term tamoxifen administration on semen analysis of oligospermie males confirms the potential therapeutic efficacy in normogonadotrophic oligospermia. 38 out of the 56 patients responded well to long-term treatment with 30 mg tamoxifen daily. According to the nomenclature of Eliasson, 32 patients reached normal sperm density and 16 patients normal sperm motility after tamoxifen treatment. In the group of responders a pregnancy rate of 34% is obtained. As far as the endocrinological parameters are concerned normogonadotrophic patients (responders and non-responders) showed an increase in testosterone, 17ß-estradiol, LH and FSH levels, whereas the levels of prolactin and testosterone/estradiol-binding globulin remained unchanged. No alterations at all were seen with regard to semen volume, during the time of tamoxifen treatment.