Forty-six tibial fractures in 44 children, which were treated by external fixation at our institution between 1 January 1991 and 31 December 1999, were retrospectively identified. Twenty-nine fractures were treated with monolateral fixation and 16 were treated with circular fixation. The average age of the patients was 11 years 8 months (range 3 years 11 months-17 years 7 months). External fixators were left in place for a mean of 13.7 weeks (range 9-33 weeks). Eleven significant complications occurred. Loss of reduction necessitating return to the operating room occurred in four patients (13%) and malunion occurred in an additional patient with monolateral fixators. Four of these patients had comminuted fracture patterns. All of the patients with loss of reduction were 12 years of age or older. No patient with a circular fixator developed mal-alignment. Final alignment in 45 of the 46 fractures was acceptable. External fixation is a safe and effective method of treating unstable diaphyseal tibia fractures in children. Patients over the age of 12 years, particularly with comminuted fracture patterns may be more effectively treated with circular external fixation or, if treated with monolateral fixation, require close observation.