A multicenter, prospective, randomized, double-blind, placebo-controlled clinical trial was conducted to test the efficacy of a specifically programmed, low-intensity, non-thermal, pulsed ultrasound medical device for shortening the time to radiographic healing of dorsally angulated fractures (negative volar angulation) of the distal aspect of the radius that had been treated with manipulation and a cast. Sixty patients (sixty-one fractures) were enrolled in the study within seven days after the fracture. The patients used either an active ultrasound device (thirty fractures) or a placebo device (thirty-one fractures) daily for twenty minutes at home for ten weeks. The two types of devices were identical except that the placebo devices emitted no ultrasound energy. Clinical examination was performed and radiographs were made at one, two, three, four, five, six, eight, ten, twelve, and sixteen weeks after the fracture by each site investigator. The time to union was significantly shorter for the fractures that were treated with ultrasound than it was for those that were treated with the placebo (mean [and standard error], 61 +/- 3 days compared with 98 +/- 5 days; p < 0.0001). Each radiographic stage of healing also was significantly accelerated in the group that was treated with ultrasound as compared with that treated with the placebo. Compared with treatment with the placebo, treatment with ultrasound was associated with a significantly smaller loss of reduction (20 +/- 6 per cent compared with 43 +/- 8 per cent; p < 0.01), as determined by the degree of volar angulation, as well as with a significant decrease in the mean time until the loss of reduction ceased (12 +/- 4 days compared with 25 +/- 4 days; p < 0.04). We concluded that this specific ultrasound signal accelerates the healing of fractures of the distal radial metaphysis and decreases the loss of reduction during fracture-healing.