Introduction of tyrosine kinase inhibitors (TKIs) in the therapy of chronic myeloid leukemia have been significantly improved the results of the treatment and prognosis of CML patients. Despite of high efficacy of TKIs therapy, resistance is developing in substantial percentage of patients, which accounts for up to 40% after several years of treatment. There are several identified mechanisms of resistance to TKIs. The presence of ABL kinase domain point mutation, which could be detected by molecular methods is one of them. The aim of the study was to screen 60 CML patients resistant to TKI therapy for the presence of ABL point mutation. ABL mutation was detected in 19 (31,6%) patients. In four cases with detected mutation the disease has progressed to blast crisis. Investigation of ABL mutation occurrence can help in finding the cause of resistance to TKI therapy in some patients suffering from CML.