Drug resistance is inevitable phenomenon in chronic myeloid leukemia (CML) patients who have received imatinib (1M) therapy. The main mechanism is point mutations in A TP-binding domain of BCR/ABL. We conducted a study on 47 IM-resistant CML patients at The Blood Transfusion and Hematology Hospital in Ho Chi Minh city using DNA sequencing method. Mutations were detected in 20 patients (42.6 percent), including 30 different types of known mutations at 14 amino acid residues. There were 4 primary IM-resistant patients (8.5 percent), all of them harbored strong-resistant mutants at P-Ioop and T3151. In total, mutations at P-loop and T3151 were 33.3 percent and 10 percent, respectively. In hospital, detection of mutations in BCR/ABL gene is valuable for selecting suitable treatment for IM-resistant CML patients.