Summary. Morphological criteria are described for the diagnosis of papillomavirus lesions at colposcopy. Using these criteria, evidence of cervical papillomavirus infection was found in 58 (29.0%) of 200 women referred for colposcopy because of an abnormal cytology report. Directed biopsies were obtained from 152 of these patients and histological changes suggestive of papillomavirus infection were found in 47 (30.9%); additional biopsy material from 139 was studied using an immunohisto-chemical technique and human papillomavirus antigen was demonstrated in 28 (20.1%). Comparison between the colposcopic results and those obtained by histology suggests that whereas it is not possible to make a distinction at colposcopy between lesions due to papillomavirus and those of cervical intraepithelial neoplasia, it is possible to identify those epithelial abnormalties that are most likely to be associated with a papillomavirus infection.