Malignant mesothelioma (MM) generally occurs as a pleural tumour, related to the inhalation of asbestos fibres. It is highly aggressive and largely unresponsive to treatment. The incidence of MM is particularly high in Western Australia because of the extensive blue asbestos mining operations that occurred in the north of the state until 1966. MM is unusual in that mutations in the tumour suppressor gene p53 are rarely observed, whilst over-expression of p53 protein is common. As the level of antibodies directed against p53 is thought to be of prognostic value in some cancers and as MM is known to be immunogenic, we studied a cohort of Western Australian patients to determine the prevalence of anti-p53 antibodies and their value as diagnostic markers or prognostic indicators. 6/88 (7%) of patients had high titres (>2 SD above the mean of controls) of anti-p53 antibodies. There was no correlation between antibody titre and survival. Although 3/38 (8%) of sera obtained from patients exposed to asbestos but prior to a diagnosis of MM contained antibodies, the same proportion of sera obtained from patients exposed to asbestos but who remained disease free also contained antibodies (2/40; 8%). Sera collected sequentially demonstrated a profound temporal stability in the titre of anti-p53 antibodies in patients with MM throughout the course of their illness. These results show that anti-p53 antibodies are observed only at a low frequency in the sera of MM patients and where they do occur, their elicitation is an early event that may be unrelated to antigen load. The occurrence of anti-p53 antibodies does not serve as either a useful prognostic or diagnostic indicator in MM. (C) 2001 Cancer Research Campaign http://www.bjcancer.com.