Infections with specific types of human papillomavirus (HPV) have emerged as necessary but not sufficient factors in the development of the majority of cervical cancers. The infection by human cytomegalovirus (HCMV) has also been implicated in both cervical intraepithelial neoplasia (CIN) and cancer. In order to test prevalence of these viral pathogens in genital lesions with suspect cytopathic changes after observation of smears, cervical biopsies from 131 patients were obtained under colposcopic guidance. The biopsies were tested for the presence of HPV and HCMV by the in situ hybridization technique using biotinylated DNA probes on paraffin-embedded sections. Presence of HCMV is twice more frequent in women with HPV-induced cervical lesions (40%) than in women with any detectable HPV (20%). It may be concluded that HCMV might contribute as one synergistic factor in the development of cervical dysplasia.