Lithotripsis using shock waves generated extracorporeally was administered to 46 patients with pseudarthrosis or delayed union of long bone fractures. From 1500 to 3000 high energy shock waves were administered one time only on an outpatient basis. Anesthesia was not required. No complications were observed. Complete recovery was obtained in all 25 patients with delayed union, and in 12 of the 21 patients with pseudoarthrosis (57%). The initiation of callus formation was observed 6-12 weeks after treatment. These results confirm that bone union can be stimulated by shock waves. The treatment procedure, advantages, contraindications and reasons for failures are discussed. This method appears to be a valuable supplement to the treatment of bone union disturbances.