Eighty-eight cases of subclinical human papillomavirus (HPV) vulvar infection were detected in a consecutive colposcopic series of 968 women. Three patterns of acetowhite lesions had a 72% predictive value (88/122) for histologically assessed HPV. The prevalence of subclinical vulvar HPV in self-referred patients was 7.9% (73/918); it was 9% (88/968) in the overall series and significantly higher in younger patients (age less than 25 years: 21/106, or 19.8%) or in those with cervical HPV or cervical intraepithelial neoplasia (CIN) (40/100, or 40%). Routine inspection of the vulva after acetic acid lavage in association with a Papanicolaou test might help identify Papanicolaou-test-negative patients at high risk of developing cervical HPV or CIN. Treatment with beta-interferon (2,000,000 IU daily intramuscularly for 10 days) was given to 30 consecutive patients, but the results were poor: regression was observed in only 2 cases.