The levels of estrogen receptors in human benign prostatic hypertrophy and in various pathological classifications of prostate carcinoma were assessed using immunohistochemical methods. All cases of benign hypertrophy showed elevated levels of estrogen receptor, while receptor-positive cells were detected in only 48% of carcinomas, indicating a negative correlation between receptor status and malignancy. Furthermore, the prognosis for effective endocrine therapy was poor in cases where tissues demonstrated low or negative receptor levels. In addition, the estrogen receptor status was compared to cell kinetic index such as proliferating cell nuclear antigen and argyrophilic staining of the nuclear organizer region.