Human papillomavirus (HPV) typing and quantitation by polymerase chain reaction was performed on exfoliated cells from 133 women referred for colposcopy because of an abnormal smear. High levels of HPV 16 correctly predicted cervical intraepithelial neoplasia (CIN) grade II-III in 93% of its occurrences, but only 59% of cases of CIN III were associated with high levels of this type. Eighty-four per cent of CIN III lesions contained high levels of at least one of HPV types 16, 18, 31, 33 and 35, but the other types were less specific for CIN III than HPV 16. Overall HPV testing compared favourably with cytology for predicting high-grade CIN lesions, but it would appear that some combination of the two modalities will produce better performance than either alone. In particular, HPV testing appears to be helpful in determining which women with mildly abnormal smears have high-grade underlying lesions in need of immediate referral for colposcopy.