Promoter hypermethylation is a marginal approach to inactivating tumor suppressor genes in cancer. DNA hypermethylation is a well-recognized epigenetic malfunction observed in several malignancies, most predominantly in prostate cancer. Aberrant DNA methylation patterns are considered to be the earliest somatic genome changes in prostate cancer. The function of promoter hypermethylation in malignant transformation of the prostate has been widely studied, from its presence in benign hyperplasia (BHP) to development and to the advanced stages of tumor formation. In the present study, we examined the promoter hypermethylation status of the glutathione S-transferase P1 (GSTP1) and RASSF1A genes in 45 BHP samples, 50 proven prostate tumor samples and 80 normal samples. Hypermethylated GSTP1 was found in 29/50 (58.0%) prostate carcinoma cases and 12/45 (26.6%) BHP cases. The RASSF1A gene was methylated in 17/50 (34.0%) prostate cancer samples and 7/45 (15.5%) BHP samples. On the basis of these findings, we propose that the epigenetic regulation of the GSTP1 and RASSF1A genes through promoter hypermethylation may play a crucial role in the progression of prostate cancer, and has probable involvement in BHP.