OBJECTIVES: The study was undertaken to describe the presenting features of children with physeal separation of the distal humerus and review the radiographic features of the diagnosis. METHODS: The charts of all children with elbow injuries aged 3 or younger were reviewed to find those with distal humerus physeal separation. Presenting complaint, initial diagnosis, and time to correct diagnosis were recorded. RESULTS: Of 101 children aged 3 or younger with elbow fractures, 7 were noted to have distal humerus physeal separation. All patients presented with pain, swelling, or disuse. Two cases resulted from suspected or confirmed nonaccidental injury. In no case was a diagnosis of distal humerus physeal separation assigned by the emergency physician or radiologist. Delay in assignment of final diagnosis ranged from 2 to 14 days. CONCLUSIONS: Physeal separation of the distal humerus is an unusual injury but accounts for a significant number of elbow fractures in children 3 or younger. Attention to the radiographic relationship of the ulna and humerus and an appropriate index of suspicion are keys to diagnosis. Nonaccidental injury should be considered as an etiology. © 2007 Lippincott Williams & Wilkins, Inc.