The SK-v cell line, established from a precancerous lesion (a vulvar intraepithelial neoplasia), contains 10 to 20 copies of the human papillomavirus type 16 (HPV16) genome, and was previously shown to derive from a clone of cells present in the patient's lesions. By in situ hybridization the integrated HPV16 DNA sequences were localized to a single site in chromosome region 12q14-q15. The localization of viral sequences to a single nonrearranged chromosome 12 suggests that integration occurred at this site in the patient's premalignant lesions. The INT1 and GLI protooncogenes are located in this chromosomal region. No detectable modification of the structure and expression of these genes was observed by blot hybridization experiments.