Chronic, nonhealing, cutaneous ulcers are a serious clinical problem. The results of previous studies using platelet-derived wound healing formula (PDWHF), derived from autologous platelets, provided evidence that PDWHF actively stimulates repair of the wound. To test whether or not PDWHF accelerates repair, a prospectively randomized, blinded trial was conducted using a placebo control. A total of 32 patients with chronic, nonhealing, cutaneous wounds of the lower extremity were randomized and treated for eight weeks with PDWHF or placebo. Epithelialization of the wound was the end point of study. In the group who received treatment, 81 per cent of patients had epithelialization in eight weeks compared with 15 per cent in the control group (p less than 0.0001). After crossover to treatment with PDWHF, all of the patients in the control group had epithelialization in an average of 7.1 weeks. Regression analysis of the rates of epithelialization also showed significant differences during the initial eight week trial and showed no difference after crossover of the control group to therapy with PDWHF. Results from this study demonstrate a highly statistically significant effect of topically applied platelet-derived growth factors on the repair of chronic, nonhealing, cutaneous ulcers.