The polymerase chain reaction (PCR) and allele specific oligonucleotide (ASO) hybridization have been used to investigate the incidence of N-ras mutation in acute myeloid leukemia (AML). The prognostic significance of these mutations and their value as markers of minimal residual disease have also been assessed. Mutated N-ras alleles were detected in 9 of 69 AML patients (13%). No significant difference in survival or remission duration was found between those patients with an N-ras mutation and those without. Four patients with N-ras mutations at presentation were followed through disease progression. The results showed no consistent pattern of association between the presence of an N-ras mutation and disease state.