Mesenteric venous thrombosis (MVT), an uncommon but important clinical entity, is one possible cause of ischemia or infarction of the small intestine. Diagnosis of this condition is sometimes difficult and treatment is often delayed because patients usually present with nonspecific abdominal symptoms. The hallmark is pain that is out of proportion to the physical findings. We report two cases of MVT, where the patients initially presented with vague abdominal symptoms. Diagnosis was made on the basis of computed tomography of the abdomen showing thrombus within the superior mesenteric vein. A search for a precipitating condition revealed no evidence of a hypercoagulable state, myeloproliferative disorder, or malignancy. These cases illustrate well the nonspecific clinical presentation of MVT. A high index of suspicion, recognition of known risk factors, or a previous history of venous thrombosis coupled with a history of nonspecific abdominal symptoms should alert clinicians to the possibility of MVT. Early diagnosis and prompt anticoagulation are the mainstay of therapy unless there are signs of peritonitis that necessitate surgical resection of the infarcted bowel.