329A case of acute monocytic leukemia (AMoL) by French-American-British (FAB) classification in a 63-year-old male showed the abnormal karyotype 46,XY,t(11;17)(q23;q21), previously reported as a variant translocation in acute promyelocytic leukemia (APL). Fluorescence in situ hybridization (FISH) analysis identified a mixed lineage leukemia (MLL) gene rearrangement, but not visible disruptions of promyelocytic leukemia (PML) or retinoic acid receptor alpha (RARA) genes. We suggest that a certain gene proximal to RARA was rearranged in this case onto a gene close to MLL on chromosome 11q. Now, a few cases of AMoL with a similar translocation have been reported in the literature, and these cases emphasize the importance of cytogenetic and FISH studies in addition to morphology, cytochemistry, and immunophenotype in classifying acute myeloid leukemia (AML).( Korean J Lab Med 2006;26:329-33)