Cervical samples from 270 women referred by area physicians were analyzed for the presence of human papillomavirus (HPV) types 6, 11, 16, and 18 by the polymerase chain reaction (PCR) followed by Southern hybridization. Samples from 154 patients were concurrently analyzed by a commercial filter hybridization technique (Virapap and Viratype Kits, Life Technologies, Bethesda Research Labs, Gaithersburg, MD). The sensitivity of the Southern blot procedure combined with PCR was significantly higher than that of the Virapap and Viratype methods. HPV was detected in 67% of women who had positive results for dysplasia by PCR and in 47% by the Virapap method. HPV types 16/18 were found more commonly than types 6/11 in every diagnostic category. More than one HPV type was detected in 12% of HPV-positive patients. The prevalence of HPV in cytologically negative or indefinite patients as measured by PCR was 22% and 40%; in contrast, by the Virapap method, these values were 7% and 10%. These results demonstrate that PCR combined with Southern hybridization provides a higher level of sensitivity than methods that use hybridization without amplification of HPV DNA and also show that the prevalence of HPV is highest in cytologically positive smears.