We report a case with typical clinical features of acute promyelocytic leukemia (APL) carrying an atypical chromosomal aberration involving chromosomes 15, 17, and 18. Molecular analysis using Southern blot hybridization and reverse transcriptase-polymerase chain reaction (RT-PCR) proved the creation of the PML/RAR alpha fusion gene in this case. These findings support the notion that this fusion is of crucial importance to leukemogenesis of APL.