Mutations at codon 12, 13, and 61 of the HRAS, KRAS, and NRAS genes were evaluated in 99 cases of pediatric acute myeloid leukemia (AML) using oligonucleotide hybridization to polymerase chain reacted derived products. Twenty-four mutations were identified in the NRAS gene, 13 in the KRAS gene, and none in the HRAS gene. The mutations occurred in a broad spectrum of cases, and there was no specific association of RAS gene mutations with patient subsets defined on the basis of clinical or hematologic features. These data demonstrate that RAS gene mutations are at least as common in childhood AML as in adult AML and suggest that RAS gene mutations play a role in myeloid neoplasia in both age groups.