In order to determine the relevance of the p53 tumor suppressor gene mutations in acute myelogenous leukemia (AML), we analyzed the p53 gene in genomic DNA of 18 unselected cases of AML by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and direct sequencing. We detected three cases (16.7%) with the p53 gene mutations showing only the mutant alleles; the high incidence in cases with loss of a whole chromosome 17 (two of three) contrasted with the low incidence in cases without abnormalities of chromosome 17 (one of 15). These cases containing the mutations of the p53 gene showed a poor prognosis. Although we analyzed a rather small series of patients, these findings suggest that the p53 gene mutations might be involved in the progression and prognosis of at least some cases of AML.