40 leg ulcers were treated for 6 weeks by application twice a day of a 20% benzoyl peroxide lotion. Each ulcer was regularly measured and its bacterial flora was determined. Therapeutic results were very satisfactory: the average healing rate of the ulcers was 62.8% of the initial wound area after 4 weeks of treatment and 76.5% after 6 weeks of treatment. The bacterial flora of the ulcers changed during treatment, streptococci and staphylococci disappeared. Pseudomonas aeruginosa became abundant.