The efficacy of imatinib mesylate has been demonstrated in patients with chronic phase of chronic myeloid leukemia (CML) as well as in advanced phase disease. The aim of this study was to evaluate the molecular response to 12 months of imatinib treatment as assessed by logarithmic reduction in BCR-ABL transcription levels, in Turkish chronic phase CML patients. Seventy-seven chronic phase CML patients were included in this multicenter, retrospective study. All patients received 12 months of oral 400 mg/day imatinib treatment. Hematological, major molecular and complete molecular response rates were evaluated after 12 months of treatment. In addition, neutrophil alkaline phosphatase (NAP) activities before and after treatment of 15 patients were also analyzed.