Acute promyelocytic leukemia (APL) is a malignant condition characterized by t(15;17)(q22;q12), which fuses the PML gene on chromosome 15 to the retinoic acid receptor alpha (RAR alpha) gene on chromosome 17. In this study, t(15;17) was identified cytogenetically by using the conventional cytogenetic technique, and its molecular counterpart RAR alpha/PML fusion on chromosome 17 on interphase nuclei was further confirmed by means of dual color- (DC-) fluorescence in situ hybridization (FISH) on serial bone marrow (BM) and peripheral blood (PB) samples from APL patients at different stages of the disease. Overall, our findings indicate that interphase DC-FISH analysis can be a useful technique as an adjunct to conventional cytogenetic investigation for detecting the presence of RAR alpha/PML fusion in APL.