The purpose of this study was to determine if there is an anatomic basis for development of the avascular necrosis infrequently seen after elbow trauma. The microcirculation to the distal humeral epiphyseal cartilage was studied in 38 elbow joints from 19 skeletally immature individuals. The findings of this study were as follows: (1) Vascularity is centripetal within the epiphyseal cartilages of the capitellum, trochlea, and medial and lateral epicondyles. Because of this vascularity pattern, it is not easy for avascular necrosis to develop after trauma within these epiphyses. (2) Vascularity is longitudinal in the epiphyseal cartilage between the capitellum and trochlea. The longitudinal vessels appear susceptible to fractures around the elbow in childhood. (3) A rich vascular network exists in the olecranon fat pad, and a vascular arch forms from the vascular network adjacent to the distal humeral epiphyseal cartilage. The vascular arch sends several large branches into the epiphyseal cartilage in a vertical fashion. Disruption of either the longitudinal intraosseous vasculature (vertical extraosseous blood supply) or the vascular arch in more than 2 places may lead to selective avascular necrosis of the epiphyseal cartilage between the capitellum and trochlea. These findings suggest vascular compromise as a possible explanation for 'fish-tail' deformities seen as sequellae of different fracture patterns.