Non-insulin dependent diabetes mellitus is a common complication of diseases of iron overload such as haemochromatosis; 53-80% of patients with haemochromatosis develop diabetes. 1 The development of diabetes in haemochromatosis is related to the magnitude of the excess iron. 1 In a cross sectional, population based study of over 1000 middle aged men in eastern Finland we found that fasting concentrations of serum insulin and blood glucose were raised in men with high serum concentrations of ferritin (an indication of raised stores of iron). 2 Iron is a catalyst of free radical stress, and it has been suggested that free radicals and lipid peroxidation play a part in the aetiology of diabetes. 3 Formation of hydroxyl radicals catalysed by iron may play an important part in the development of diabetes since the cells that produce insulin are extraordinarily sensitive to damage from oxidation. 3 In another cohort study low plasma concentrations of vitamin E were associated with an increased incidence of diabetes, which supports this theory. 4 There are, however, no other studies of the association between iron stores and the incidence of diabetes in a healthy population.