The purpose of this study was to determine the frequency with which inversion of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV) is seen at ultrasound (US) in children with malrotation. Nine patients with malrotation at upper gastrointestinal (UGI) radiographic examination (surgically confirmed) were studied prospectively. Anatomic relationships between the SMA and SMV were evaluated with real-time US in an axial projection, with the transducer placed at the midline of the anterior abdomen. Use of duplex imaging confirmed which vessel was the artery and which was the vein. Vessels were considered to be inverted if the SMV was left of the left lateral margin of the SMA. The SMA and SMV were inverted in six patients (67%) and were normal in three (33%). One patient with normal mesenteric vessels had midgut volvulus; duodenojejunal resection was required. Inversion of the SMA and SMV at US is not sufficiently sensitive to screen patients for malrotation. UGI examination remains the standard modality to diagnose this disorder.