Expression of the tumour suppressor gene p53 was examined in squamous cell carcinoma of the head and neck using two p53 antibodies, PAb 421 and PAb 1801. Elevated p53 expression was found in 67% of the 73 patients investigated. P53 expression was not found to correlate with whether the patient had been previously treated or not, nor any of the clinico-pathological parameters. However a correlation was found between the patients smoking history and positive p53 staining. Six out of seven non-smokers did not express p53 whereas 29 of 37 heavy smokers were found to have elevated p53 expression (P less than 0.005). Also, of a group of ten patients who had given up smoking more than 5 years ago, nine had elevated expression. Epidemiological studies have shown a correlation between heavy smoking and head and neck cancer. The present study indicate a genetic link for this correlation.