Imatinib mesylate, a selective tyrosine kinase inhibitor, has been shown in preclinical models and preliminary clinical trials to have activity against this tumors. Method: We conducted a retrospective, descriptive study of 90 patients diagnosed with advanced gastrointestinal stromal tumor in Cancer hospital from August, 2007 to July, 2010 to evaluate the efficacy and safety of Imatinib mesylate. Result: Overall, 20% of patients had complete response, 33.3% of patients had partial response with Imatinib 400 mg / day, 40% had stable disease while progressive disease covered 6.7% cases.