One hundred and thirty seven cases of paraffin-embedded tissue specimens biopsied each from condylomata and pseudo-condylomata of vulva and vagina were examined. Type 6b 11 human papillomavirus (HPV) DNA was detected in condylomata by in situ hybridization using digoxigeninlabelled probes and polymerase chain reaction (PCR). The positive rate was 82.5%, 83.9% respectively. It was negative in the 137 cases of pseudo-condylomata by in situ hybridization, but positive in 3 cases by PCR. For a correct diagnosis, the necessity of combining the data of clinical finding, microscopic examination and in situ hybridization or PCR is emphasized. Our results showed that pseudo-condylomata represent dysplastic appearances of vulval and vaginal mucosa, which become more marked during pregnancy and fungal or trichomonal infections, and could rather easily be misdiagnosed as condylomata.