Diabetes developed in 14% Europeans, 33% Indian Asians and 30% African Caribbeans between baseline (mean age:51.8±7.0) and follow-up (mean age:70.5±6.3). Mid-life measures of insulin resistance, and of upper body fat deposition, were already unfavourable in people who developed diabetes a decade or so later, and were more adverse in the ethnic minorities. Insulin resistance at baseline contributed most to explaining the ethnic minority excess of diabetes in both sexes. Of obesity measures, adjustment for truncal fat provided the most consistent and independent attenuation of the ethnic differentials in both sexes- indeed. adjustment for truncal fat largely explained the ethnic differential in diabetes incidence in women, but in men however, a two-fold excess risk of diabetes remained after adjustment for family history, conventional lifestyle and cardiometabolic risk factors. Our findings suggest that further study of risk factors throughout the life-course and/or a search for novel risk factors is required if we are to understand why ethnic minority groups are at such high risk of developing diabetes.