In the present study, the expression of type IV collagen associated with the basal membrane (BM) was studied histochemically (indirect immunoperoxidase-antiperoxidase) in cervical human papillomavirus (HPV) lesions (diagnosed using in situ DNA hybridization) of different grades. The expression of type IV collagen in premalignant epithelial lesions (HPV with and without cervical intraepithelial neoplasia) was identical with that in the BM of normal exocervical epithelium, in contrast to 60% (3/5) of carcinoma in situ lesions and 90% (10/11) of invasive carcinomas, where the staining pattern was interrupted and the staining intensity reduced. Thus, the expression of type IV collagen seems to remain unchanged during the entire spectrum of premalignant stages of cervical HPV lesions. This suggests that the squamous epithelial cells responsible for the formation of the BM are not affected by this virus at early stages of the disease, and immunohistochemical recognition of an intact staining pattern of type IV collagen may signify well-preserved basal cell function (confined to nonmalignant?) HPV-infected squamous epithelium.