Evidence that oxygen free radicals may be contributory to further tissue damage in the events following cutaneous thermal injury supports a role for interventional therapy using antioxidants. However, previous work has relied almost entirely on animal-based models with little clinical information available. Also, methods used to support an oxidative role in thermal injury have relied almost exclusively upon the use of lipid peroxidation studies. Further work substantiating a contributory role of free radicals is therefore required using additional methodology before considering antioxidant therapy aimed at retarding tissue damage. We investigated general oxidative damage to protein in burn blister fluid by quantifying the protein carbonyl levels from 11 patients admitted with superficial or partial thickness burns. Total antioxidant capacity was also assessed, together with measurement of protein and the antioxidants uric acid and bilirubin. Data were compared with values obtained for serum in healthy volunteers. Following thermal injury, burn blister fluid protein carbonyl level was increased by almost 50 per cent (P = 0.005) compared with normal serum. Antioxidant scavenging capacity, protein and bilirubin were all significantly reduced, but uric acid unaltered compared with control values. The present data support a role for oxidative damage in cutaneous thermal injury.