Many studies have shown a strong correlation between CIN and HPV infection. Molecular biology has allowed identification of types of HPV which seem to be connected, more frequently than others, to dysplastic lesions. Physical state of HPV-genome seems to play an important role in the development of cervical cancer. In this study the HPV-genome has been searched in tissue specimens obtained from 34 women affected by CIN II and III. All patients underwent laser conization. Immediately before treatment, colposcopically directed biopsies of the cervical lesion and of the areas with no colposcopically apparent disease were taken and on these samples, HPV-DNA has been searched, isolated and analysed for HPV types and physical state. Histologic examination on cones showed 6 cases of CIN II (3 with HPV), 24 cases of CIN III (14 with HPV), 1 microinvasive carcinoma and 3 with no residual lesion. Southern blot analysis detected HPV-DNA in 4 cases of CIN II (16.7%) and in 20 cases of CIN III (70.6%). In 50% of CIN II and 85% of CIN III HPV 16 DNA has been found and in the remaining 50% of CIN II and 15% of CIN III HPV 31 DNA has been detected. All CIN II and 14 cases of CIN III showed episomal HPV-DNA. Integrated HPV-DNA has been found in 3 cases of CIN III and the other 3 cases of CIN III showed both integrated and episomal HPV-genome. Integrated form has been noticed only for HPV 16 type. In no case of colposcopically normal tissue has HPV-DNA been found. These data seem to confirm the strong correlation between HPV 16 type, which often has integrated form, and CIN III strengthening the hypothesis of its potential oncogenic action.