Two cases of superior mesenteric vein thrombosis were examined with computed tomography. Prior to the operation the CT appearances of the disease were, as follows: focal thickening of the bowel wall, gas and fluid collection in the dilated bowel, mesenteric leaf, a little ascites and dilated superior mesenteric vein with central filling defect. We conclude that CT scan is very useful for an early diagnosis of the superior mesenteric vein thrombosis.