The treatment of delayed and nonunion of fractures by a single extracorporeal dose of high energy shock waves generated in a water medium and focused on the fracture site is reported. The shock waves break up sclerotic bone by producing microfissures and numerous bony fragments because of the difference in impedance between bone (and calculi) and soft tissues. Osteogenesis is stimulated and contributed to union in 70 out of 82 fractures within a reasonable time. Treatment was given as an outpatient with regional anaesthesia; there were no side effects or complications.