In a randomized controlled clinical trial, the properties of low-frequency ultrasound in the treatment of chronic venous ulcers were investigated. Thirty-eight patients with chronic ulcerations of the legs caused by chronic venous insufficiency were randomly assigned to receive either conventional therapy alone or conventional therapy plus additional 30 kHz ultrasound treatment. Patients with other conditions that may impair wound healing such as diabetes mellitus or arterial disease were excluded. The ultrasound treatment consisted of 10 minutes of foot bathing with application of 30 kHz ultrasound 100 mW/cm(2) three times a week. Response was evaluated with the use of planimetry of the ulcer area and compared with controls after 3 and 8 weeks. After 3 weeks of treatment (and to a greater extent after 8 weeks of treatment) the ultrasound group showed a markedly better response than the control group. Although the control group showed a mean decrease of 11% in the ulcerated area after 8 weeks, in the ultrasound group the mean ulcerated area decreased by 41% (p < 0.05). There were only mild side effects in some of the patients treated with ultrasound. In conclusion, application of low-frequency ultrasound may be a helpful treatment option in chronic venous leg ulcers.