We investigated aberrant p53 expression in 81 cases of cervical intra-epithelial neoplasias (CIN) using a polyclonal antibody CM-1. The presence of human papillomavirus (HPV) DNA was evaluated by in situ and dot blot hybridization. Significant (more than 1% of cells positive) p53 positivity was found in three cases (4%) of which only one contained HPV DNA. In an additional nine cases, occasional p53 staining was found in basal epithelial cells, frequently associated with epithelial hyperplasia and increased subepithelial inflammation. The results show that aberrant p53 expression is an infrequent finding in CIN lesions. It can be seen in lesions both with and without HPV infection. Most importantly, there was no p53 expression in most cases of HPV-negative CIN, suggesting that p53 inactivation is not an obligatory step in the development of cervical dysplasia. However, our findings do not exclude the possibility that p53 mutations can occur later in the course of cervical carcinogenesis.