The prognosis of metastatic or recurrent GISTs is poor, because these tumors resist chemotherapy and radiotherapy. We report a patient with recurrent GIST who underwent molecularly targeted therapy with imatinib, a novel oral tyrosine kinase inhibitor. A 64-year-old man presented with large intra-abdominal mass. The patient had a history of jejunostomy with colostomy for intestinal GIST. The abdominal mass was phi3 x 3.5 cm in size with ascites at Douglas, as determined by computed tomography, and was diagnosed as a peritoneal relapse of GIST. Treatment with imatinib daily was started. After 1 month of treatment with imatinib, reduction of the abdominal tumor began to be recognized on palpation. Computed tomographic scanning at 11 months revealed that the tumor had completely disappeared. The major side effect was drug eruption,which was easily manageable with 2 weeks drug holidays. Imatinib shows promise as a safe and effective drug for the treatment of patients with recurrent GISTs.