The purpose of this study was to examine the effect of focused extracorporeal shock wave therapy (ESWT) on the treatment of nonunions. As part of a prospective study, we included 143 patients (average age, 41.4 years) with a diagnosis of nonunion (mean, 14.1 months; range, 6-84 months). High-energy shock wave treatment was applied using shock wave generator. The shock waves were applied in 3-5 sessions of 2500 to 3000 impulses each given at 0.25-0.84 mJ/mm(2), at intervals of 48-72 hours between sessions. A maximum of 3 cycles of treatment was given, at 3-month intervals. The patients were followed during a 12-month period until fracture healing or, in case of failure, until another therapy was adopted. Complete healing was observed in 80 of 143 cases (55.9%) at an average time of 7.6 months (range 2-24 months). Partial healing occurred in 41 cases (28.7%) and no healing was observed in 22 cases (15.4%). Patients with trophic nonunions had a better success rate than patients with atrophic nonunions (P<.05). The results show extracorporeal shock wave therapy is a safe and effective treatment for nonunion. ESWT is more effective for trophic nonunions than atrophic nonunions.