Purpose To investigate the characteristics of nonunion and avascular necrosis following phalangeal neck fracture in children. Methods A cohort of all pediatric phalangeal neck fractures complicated by nonunion, with or without avascular necrosis of the phalangeal head, over the last 10 years was reviewed retrospectively. The following data were documented: age, gender, fracture site, mechanism of injury, fracture type, presence of digital ischemia, initial management, and outcome. Results Our database of phalangeal neck fractures in children over the last 10 years included 215 fractured digits. Of these, 4 developed nonunion (group A) and 8 developed nonunion with avascular necrosis (group B). All patients in group A were young children (mean age, 2.5 y) with fractured thumbs, initially managed by closed reduction and splinting. The fractures redisplaced and failed to unite, resulting in instability that was later treated by bone grafting and stabilization with a K-wire. Patients in group B were older children (mean age, 5.6 y) and 7 of 8 had finger fractures. All 8 patients presented with stiffness of the affected joint, and no further surgery was performed. Conclusions When nonunion occurs following pediatric phalangeal neck fractures, it usually affects the thumb and presents with thumb instability, and bone grafting is often required to achieve union. In contrast, avascular necrosis following phalangeal neck fractures usually affects the little finger and presents with stiffness, and hence, further surgery is not often required short term, although the long-term result after skeletal maturity is unknown. (J Hand Surg 2010;35A:1269-1274. (C) 2010 Published by Elsevier Inc. on behalf of the American Society for Surgery of the Hand.)