Twelve patients (age range: 53-78 years) with prostatic cancer were treated with Buserelin (1.2 mg/day) and cyproterone acetate (150 mg/day). Testicular biopsies performed after 13-96 weeks of treatment were compared to those obtained from 6 untreated men of similar age. Deranged spermatogenesis was observed in all but 1 treated patient. The appearance of immature Sertoli cells and atrophic Leydig cells suggests a condition of pharmacologic 'hypophysectomy'. The variable damage to the seminiferous epithelium and findings of an incomplete involution of Leydig cells suggested a decreased but still present testicular steroidogenesis.