The causal association of human papilloma virus(HPV) with cervical cancer has been supported by multiple lines of evidence. Therefore, in the case of dysplasia, the presence of HPV-DNA should be detected and its subtypes identified. This is important in the determination of the prognosis for cervical disease. We reported a study in which the localization and types of HPV in cervical diseases was identified by in situ polymerase chain reaction(PCR), using biotin-labelled DNA probes. The in situ PCR, used by us was modified of Nuovo's method. We used biopsy materials of 18 CIN and 9 SCC cases(total 27 cases), all of which had been detected HPV-DNA by Southern blot hybridization, but not detected by in situ hybridization. A positive intranuclear reaction was detected in 13 of 18 CIN cases and 6 of 9 SCC cases(total 19 positive cases). Molecular biological techniques are the most reliable methods for detecting specific tumor genes and virus DNA. In situ hybridization has the advantage of enabling recognition of the cellular localization of the DNA in histologic specimens, but its sensitivity in inferior to the other techniques such as Southern blot, Dot blot and PCR. In situ PCR method possesses the advantages of both PCR and in situ hybridization in being highly sensitive and enabling visualization of the cellular localization of the DNA. In our present study, we succeeded to detect HPV-DNA in cervical biopsies of CIN and SCC cases by the in situ PCR.