OBJECTIVES: Imatinib is a low molecular tyrosine kinase inhibitor that blocks the kinase activity KIT and PDGFRα, and a first-line drug in the treatment of unresectable and metastatic gastrointestinal stromal tumor (GIST). The standard treatment of patients with localized primary GIST is a complete surgical resection of the tumor. Several studies have shown that target therapy improves survival of patients after GIST resection.The purpose of this study was to estimate the costs and effectiveness of adjuvant imatinib therapy vs no treatment in patients who have undergone GIST resection. METHODS: A Markov model was used to estimate costs and effectiveness of adjuvant imatinib therapy in the long term follow-up period. Data on overall and recurrence-free survival were taken from the phase III clinical trial ACOSOG Z9001 and were used to assess efficacy. Measures of effectiveness include such indicators as life-years saved and quality-adjusted life-years (QALYs) gained for adjuvant imatinib following surgical resection and surgical resection only. Data on the common practice of GIST treatment in the Russian oncology centers was used in the model. Costs, life-years and QALYs gained were calculated over the 50-year time horizon and discounted at an annual rate of 5%. RESULTS: The number of life-years saved was 10.01 for imatinib treatment against 8.67 for no treatment. The number of QALYs was 7.97 and 6.82, respectively. The costs of one-year patient management  with adjuvant imatinib therapy were €44,348 per person; a patients who had not received imatinib in adjuvant mode required €32,102 per person. CONCLUSIONS: The analysis showed that adjuvant imatinib therapy is more costly compared with no treatment. However, it is more effective and can increase the life expectancy of patients. In this case the costs of therapy are partly offset by reducing the frequency of relapses and the progression of the disease.