SIR, Chronic wounds that fail to heal. eg diabetic or venous leg ulcers and pressure sores, represent a significant health care problem. The causes responsible for non-healing wounds in specitic patients are poorly understood. Deficiencies of growth factors are likely to be involved.''" In fact, a relative absence of platelet-derived growth factor (I'UCiF). one of the master'growth factors for efficient wound healing, an increase in the overall proteolytic activity, and a rednction of the corresponding protease inhibitors have heen reported in chronic wounds.''^ Even though the degradation of growth factors in chronic wounds might be responsible for the disappointing clinical trials with several recombinant growth I'ttcturs."'only limited knowledge ol'growth factor stability in ihe chriinic wound is available. We therefore analysed whether the most prominent isoform of PDGF, PDGF-AB. is degraded in wound fluid from chronic venous leg ulcers, and, il'. so. whether a loss of PDGF-AB stability can be prevented by specific protease inhibitors.