We retrospectively surveyed pediatric acute myeloid leukemia (AML) patients with multilineage dysplasia treated with the AML 99 and the Children's Cancer and Leukemia Study Group (CCLSG) AML 9805 protocols. We found only 9 AML patients (2.6%) with multilineage dysplasia among the 341 patients with newly diagnosed de novo AML. Eight of the 9 patients obtained complete remission (CR) following the intensive AML-oriented treatments. Three of 7 patients who underwent stem cell transplantation were alive in CR for more than 4 years, and the 2 patients treated only with chemotherapy were alive in CR for more than 30 months. We did not identify any particular chromosomal abnormalities or differentiation according to the French-American-British classification in these 9 patients. No reports have described AML with multilineage dysplasia in children, and the incidence of the disease is expected to be very low. We plan to conduct a prospective pathologic review to select cases with this disease entity in the next Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 protocol.