The sensitivity of human papillomavirus (HPV) detection was compared by colposcopy, histology and DNA hybridization among 304 women with abnormal Papanicolaou (Pap) smear. Colposcopically directed biopsies revealed HPV infection in 71% of cases, DNA hybridization in 35%, and both together in 78%. DNA hybridization detected HPV in 24% of the 84 benign cases with no histological signs of HPV, in 32% of the 133 condylomas verified by biopsies and in 51% of the 85 cases with intraepithelial neoplasia, 95% of which presented histological signs of HPV. The pattern of occurrence of different HPV-types resembled findings in earlier reports. HPV infection is common with abnormal Pap smears and it can be identified relatively reliably by means of cytology, colposcopy and histology. DNA hybridization serves as a complementary technique which may reveal the oncological potential of the virus.