AIM The objective of our study was to determine which ultrasound power density (0.5 W/cm(2) or 1 W/cm(2)) is more effective at reducing the area and volume of leg ulceration. METHODS A total of 65 patients with venous ulcers were randomly divided into three groups: A, B and C. In group A, 22 patients were treated with ultrasound rated at 1 W/cm(2) and with compressive therapy. In group B, 21 patients were treated with ultrasound rated at 0.5 W/cm(2) and with compressive therapy. In both groups the patients were treated with a pulsed wave of a duty cycle of 1/5 (impulse time=2 ms, pause time=8 ms) and frequency of 1 MHz. The 22 patients in group C (control group) were subjected to topical pharmacological treatment. RESULTS We found a statistically significant reduction of the ulcer area, volume and linear dimensions in all three groups of patients. The ulcer area reduction rate was highest in group B. The volume reduction rate in group B was higher than in group A only. The rate of reduction of suppurate area was highest in group B. CONCLUSION We have demonstrated that ultrasound rated at 0.5 W/cm(2) causes greater and faster changes in the healing process than ultrasound rated at 1 W/cm(2).