The purpose of this series is to describe the sonographic findings in 4 patients with intestinal obstruction due to internal hernia.Four patients had clinical features of intestinal obstruction. Sonography was performed with broadband convex and linear array transducers in these patients.In all 4 patients, there were features of intestinal obstruction with a zone of transition between dilated and nondilated bowel. There was a cluster of crowded, compressed, and aperistaltic small-bowel loops, as if they were tightly packed within a sac, by the side of this zone in 3 patients. This appearance was due to obstruction of the afferent loop caused by compression. In the last patient, there were 2 loops of dilated bowel within a sac outlined by fluid due to obstruction of the efferent loop. All 4 patients had obstructed internal hernias at laparotomy.Sonographic features of internal hernia are described.