Aims: Low-intensity pulsed ultrasound has shown acceleration of bone healing in fresh fractures. The goal of this study is to assess the effect of low-intensity ultrasound on bone healing in established nonunion cases and following osteotomy. Methods: A non randomized trial on 29 cases, located in the tibia, femur, radius/ulna, scaphoid, humerus, metatarsal and clavicle, met the criteria for established nonunions. On average, the post-fracture period prior to the start of ultrasound treatment was 61 weeks. Daily, twenty-minute applications of low-intensity ultrasound at the site of the non-union were performed by the patients at home. In a placebo-controlled, randomized clinical trial double-blinded trial, 97 adults, who had undergone an osteotomy of the lower extremity were randomly allocated an active- or placebo ultrasound device. Every two weeks the patients were examined both clinical and radiological. Results: Twenty-five of the twenty-nine non-union cases (86%) healed in an average treatment time of 22 weeks. Forty-six patients (75 bones) were treated with an active ultrasound device and 44 patients (78 bones) with a placebo device were eligible for analysis. An overall reduction of time to consolidation of 32% was established. A nonunion, which had to be treated operatively, occurred in four cases in the placebo group and in none in the active group. No other prognostic variables were found. Conclusions: Low-intensity ultrasound can stimulate bone healing in osteotomies and nonunions. In patients with a fracture or osteotomy, who are at high risk of developing nonunion, low-intensity ultrasound can be valuable as additional therapy.