In order to evaluate the expression of p53 protein in 28 premalignant and 40 malignant squamous cell proliferations of the larynx and its relationship to tobacco consumption, human papillomavirus infection and differentiation grade of the lesions, p53 expression was examined by means of a microwave post-fixation immunohistochemical method using the PAb 240 and PAb 1801 monoclonal antibodies. HPV infection was assessed by non-isotopic in situ hybridization (NISH) and polymerase chain reaction (PCR). A large proportion of carcinomas (77.5%) and dysplasias (61%) expressed p53. No difference was found between differentiation grades of the lesions regarding p53 detection (P > 0.1), but moderate or intense p53 expression was more frequent in the carcinomas (P < 0.05). A statistical correlation was found between cigarette consumption and both p53 detection and p53 staining intensity (P < 0.05 in each case). HPV study revealed HPV 16 and 18 infection only in carcinomas. The frequency was 28% and the physical state of the virus as demonstrated by NISH was integration into the genome. We observed an inverse relationship between HPV infection and p53 expression (P = 0.006). Our findings suggest that p53 overexpression is a common and early event which increases in frequency with progression of laryngeal squamous cell carcinoma. The expression of p53 is influenced by tobacco and high-risk types of HPV.