BACKGROUND Accurate measurement of BCR-ABL1 fusion transcripts is critical for therapeutic stratification in patients with chronic myelogenous leukemia (CML). Previous studies have reported the variable performance of the existing quantitative reverse transcription polymerase chain reaction (RQ-PCR). Here, we developed a one-step multiplex RQ-PCR method based on the catalytically cleavable fluorescence probe technology for quantification of BCR-ABL1 transcripts. METHODS Performance was evaluated with respect to the limit of detection (LoD), linearity, precision, and comparison on the VIIA7 Real-Time PCR system. Multiplex RQ-PCR was performed by the one-step and one-well reaction without the hands-on time. RESULTS Our assay showed a LoD of 1.5 pg with linearity in the range of more than 4 logs of dilution. Intraassay, interassay, and total percent CVs at the concentration of 150 ng were 12.8%, 22.6%, and 28.0%, respectively. The assay correlated well with Asuragen's BCR/ABL1 Quant™ kit over a 6 log concentration range (r=0.9967). CONCLUSION Our assay demonstrated comparable performance characteristics in comparison with previous RQ-PCR based on the TaqMan probe technology.We conclude that our method could be a reliable tool in the clinical setting.