We have looked at the relationship between serum urate and the molar equivalent serum antioxidant capacity (MESA) in diabetic and normal individuals who attended St Bartholomew's Hospital diabetic clinic and BUPA Health Screening Centre, London, and have compared serum antioxidant capacity between the two groups. Sample response curves showed less serum antioxidant potential in diabetics than in nondiabetics, and a linear relationship between serum urate and MESA. Simple regression analysis gave a correlation coefficient of 0.9 (p < 0.0001). Significant differences between the two groups were found for both mean MESA values (p < 0.0001) and mean uric acid levels (p < 0.005).