Infants diagnosed with acute myelogenous leukemia (AML) are likely to have subtypes M4 or M5 characterized by 11q23 abnormalities like a t(9;11)(p22;q23). Detection of all possible types of chromosomal abnormalities, including mixed lineage leukemia (MLL) gene rearrangements at 11q23, is of importance for the identification of biological subgroups, which might differ in drug resistance and/or clinical outcome. Here, we report the clinical, conventional banding and molecular cytogenetics data of a 6-month-old boy with an AML-M5 presenting with a unique cryptic rearrangement involving the MLL gene: a three-way t(9;19;11)(p11.2;p13.1;q23).