We performed light microscopic morphometry on prostate biopsies of 41 patients who underwent androgen suppressive therapy for 24 weeks with the luteinizing hormone releasing hormone (LHRH) agonist leuprolide depot for symptomatic benign prostatic hyperplasia (BPH). Before treatment started, the prostates consisted of 88.4% stroma, 9.0% epithelium and 2.6% glandular lumen. After completion of therapy, the percentages were 94.7, 3.0 and 2.3, respectively. The absolute reductions of volume were 27% for stroma, 77% for epithelium and 40% for lumen. Correlations between pretreatment parameters (epithelial content, stromal epithelial ratio and prostate specific antigen density (PSAD)) and the clinical outcome parameters (prostate volume reduction, improvement in maximum flow rate, reduction of symptom score and reduction in outflow resistance) were not statistically significant, indicating that the histological composition of BPH tissue or PSAD are poor parameters to predict differences in response for individual patients during hormonal therapy for BPH. By comparing morphometry results of the core biopsies with morphometry performed on corresponding TURP tissue, it appeared that the lumen content of the biopsies was somewhat underestimated.