In particular, we compared ddPCR QXDxTM BCR-ABL %IS Kit (Bio-Rad, Hercules, CA, USA) with LabNet-approved RT-qPCR methodologies in monitoring BCR–ABL1 levels in CML patients by assessing the agreement between the measures obtained, the repeatability (intra-laboratory variability), and the reproducibility (inter-laboratory variability) of the two methods. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.