The frequency of H-ras, K-ras, and N-ras mutations and the presence of high-risk human papillomavirus (HPV 16, 18, and 33) DNA were studied in 75 paraffin-embedded specimens obtained from 68 Japanese patients with a variety of prostate carcinomas by using polymerase chain reaction and DNA hybridization with sequence-specific oligonucleotides. Ten specimens each of normal and benign hyperplastic prostatic tissues from the same number of patients were also examined for this analysis. Of 68 carcinoma cases, ras gene mutations were present in 16 cases (24%) and HPV DNAs in 28 cases (41%). Eleven mutations were detected in codon 61 of H-ras, 4 in codon 12 of N-ras, and 2 in codon 61 of K-ras. HPV 16, 18, and 33 DNAs were found in 11, 17, and 5 cases, respectively. Eight of the 16 cases with ras mutation also harbored HPV DNAs. The frequency of ras mutations and the HPV infection increased in patients with advanced stages of the tumor and with the higher Gleason score. There was the predominant presence of H-ras codon 61.2 (CAG-->CTG) mutation and HPV 18 DNA in prostatic carcinomas metastasizing to the bone. None of the normal or benign hyperplastic prostatic specimens contained either ras mutation or HPV DNA. Our results suggest that ras gene mutations and HPV infections are relatively frequent, at least in prostate carcinoma of Japanese patients. These two factors appear to be related to the progression of the tumor. Moreover, H-ras codon 61.2 mutation and HPV 18 infection may have some predictive roles for bone metastasis in prostate carcinoma.