A case of spontaneous rupture of giant gastrointestinal stromal tumor (GIST) of stomach causing acute abdomen is described below. A male patient with abdominal mass presented with symptoms and signs of acute abdomen after admitting for 1 day. After preoperative management and evaluation, an exploratory laparotomy was performed, where rupture of a huge tumor in the stomach was found. A subtotal gastrectomy including the mass was performed and the final immunohistochemi-cal examination verified that the neoplasm was a high risk GIST. The postoperative period was uneventful and the patient received treatment with imatinib mesylate, and regular fol ow-up without recurrence.