To demonstrate the effect of a two-layered polyurethane foam wound dressing (Lyomousse) on the healing of venous leg ulcers a comparative study in 41 patients (24 treated, 17 controls) was performed. For a quantification of the process of healing a computer-assisted morphometric procedure was used. This method is based on a Polaroid-photograph of the ulceration which is transferred in digital form by means of a digitizing equipment. From the digital data the primary variables area, perimeter and maximal diameter of the ulceration are calculated. For quantitative comparison the relative changes as well as the rate of the changes of the primary variables were used. The statistical comparison of the treated group and the control group showed a highly significant (p less than 0.001) promotion of wound healing for the therapy with the synthetic foam dressing using the relative changes as an indicator, and a significant (p less than 0.05) increase in the rates of changes, indicating an acceleration of healing. This therapeutical advantage can be drawn back to specific characteristics of the synthetic material, assuring a water vapour saturated micro-environment at the surface of the wound and reducing this way the detrimental effect of heat loss due to evaporation onto the healing process.