Afferent loop syndrome(ALS) is caused by obstruction of the afferent loop after subtotal gastrectomy with Billroth II gastrojejunostomy, Prompt diagnosis of ALS is important as perforation of the loop occurs. The aim of this study is to ascertain the value of sonography and CT to diagnose ALS. We describe the radiologic findings in ten patients with ALS The causes of ALS established at surgery, included cancer recurrence(n=4). Abdominal X-ray and sonography were performed in all cases, upper GI series in five cases and computed tomography in two cases. The dilated afferent loop was detected in only two cases out of ten patients in retrospective review of abdominal X-ray. ALS with recurrence of cancer was diagnosed in three cases by upper GI series. Of the cases that had sonography. the afferent loop was seen in the upper abdomen crossing transversely over the midine in all ten patients. The causes of ALS were predicted on the basis of the sonograms in three of the five cancer atients. In two cases of computed tomography. the dilated afferent loop and recurrent cancer at the remnant stomach were seen, Our experience suggests that the diagnosis of afferent loop syndrome can be made on the basis of the typical anatomic location and shape of the dilated bowel loop in both sonography and computed tomography.