To explore the value of detection of PML/RARalpha gene rearrangement on bone marrow smears (BMS) by dual-color fluorescence in situ hybridization (D-FISH) for the diagnosis of acute promyelocytic leukemia (APL), the locus-specific probes for PML and RARalpha genes labeled directly and respectively by Spectrum Green and Spectrum Orange and the D-FISH technique were used to detect the PML/RARalpha gene rearrangement on BMS in 27 suspected APL patients. The results were compared with that of conventional cytogentics (CCG) and reverse transcriptase polymerase chain reaction (RT-PCR). The results showed that out of 18 newly diagnosed patients 14 were found having t(15;17) translocation by CCG and PML/RARalpha gene rearrangement were confirmed by BMS-D-FISH and RT-PCR. Thus, their APL diagnosis was determined; out of 4 patients in whom t(15;17) translocation was not detected by CCG, one had positive BMS-D-FISH and RT-PCR results, thus, this case was considered as having a cryptic t(15;17) translocation, three had negative BMS-D-FISH and RT-PCR results, thus, they were diagnosed as having acute myeloid leukemia rather than APL. In 9 cases with remission, one case with partial remission was found having t(15;17) translocation by CCG, and he had positive BMS-D-FISH and RT-PCR results, the other 8 patients (6 cases with normal karyotype and 2 cases without CCG examination) displayed different BMS-D-FISH and RT-PCR results: negative in 6 cases, but positive in 2 cases. The 2 cases were believed that they survived with minimal residual disease (MRD). It is concluded that BMS-D-FISH is a sensitive and reliable method for the detection of PML/RARalpha rearrangement. It is helpful for diagnosing APL and monitoring its MRD, and especially fit to those patients presenting a cryptic translocation or with failed cytogenetics, lacking suitable material for RT-PCR, as well as needing retrospective study.