We performed a prospective randomised controlled trial of the A-V Impulse System in 82 patients treated by hemiarthroplasty for subcapital fracture of the femoral neck. The incidence of proximal deep-vein thrombosis as assessed by Doppler ulfrasonography was 23% in the control group and 0% in those using the device (p < 0.01). Calf and thigh circumferences were measured in both groups at seven to ten days after operation. In the treatment group there was a mean relative reduction of postoperative swelling of the thigh by 3.27 cm (p < 0.001) and of the calf by 1.55 cm (p < 0.001). The A-V Impulse System appears to be a safe and effective method of reducing the incidence of proximal deep-vein thrombosis, and of postoperative swelling.