We used ultrasonography in ten children with pulled elbow to compare measurements of the radiocapitellar distance (RCD) on the affected and the unaffected sides. Similar measurements were made in a group of ten age-matched normal children. The mean RCD in pronation of the affected and normal sides in the patients with pulled elbows was 7.2 mm +/- 0.7 and 3.8 mm +/- 0.5, respectively (p < 0.0001). In the normal children the mean RCD in pronation was 4.5 mm +/- 0.5. We conclude that ultrasonography is of value for documenting pulled elbow in children.