The effect of androgen blockade on the normal human prostate was studied in 16 healthy volunteers opting for male-to-female gender reassignment. Their ages ranged from 19 to 27 years. After 8 weeks of treatment with Anandron, serum hormone levels indicated anti-androgenic action and physical signs of feminization appeared. Prostate volumes (measured by ultrasound) before and following Anandron treatment remained the same. After 18 months of treatment with cyproterone-acetate and ethinyl estradiol, prostate volumes again were not changed. However, histology revealed glandular atrophy and an increase in stromal tissue. The significance of these findings is discussed.