The purpose of this study was to investigate the use of elbow arthrography for detecting an occult subluxation of the radial head and for verifying the quality of reduction in children with ulnar fractures. The study involved 15 children who underwent closed reduction (with or without percutaneous pinning) based on arthrography for minimally displaced fractures with or without radial head subluxation. The mean age of the patient at the time of surgery was 6 years (range, 3–12 years). Initial diagnoses based on conventional radiographs were compared with arthrographically confirmed final diagnoses in groups of children with ulnar fractures of the olecranon, proximal, and diaphysis. Arthrography confirmed initial radiographic diagnoses in 10 and altered diagnoses in five patients. We conclude that arthrography can be useful for detecting an occult subluxation of the radial head and for evaluating adequate reduction in children of less than 6 years with ulnar fractures.