A polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) assay was used to identify the exons which contained point mutations in the conserved regions (exons 4-8) of the p53 gene in 49 acute myelogenous leukaemia (AML) patients. SSCP analysis in our study was consistent with the results of subsequent direct DNA sequencing in detecting point mutational change in exons 5 and 8 of one AML patient and in exons 7 and 8 of two additional AML patients. The mutations were located at codons 245 and 273, which have been found in many other tumours, and codons 178 and 290, which have not been reported previously. All of the p53 proteins in which we detected point mutations were immunoprecipitated by the p53 monoclonal antibody PAb 240, which has been shown to recognize a mutant conformation of p53 protein. Thus, our results indicate that functional inactivation of the p53 gene by point mutational change might be one of the mechanisms underlying disease progression of AML.