To determine the relations of diet with risk of clinical noninsulin-dependent diabetes, we analyzed data from a prospective cohort of 84360 US women. During 6 y of follow-up we identified 702 definite incident cases. Because body mass index (BMI) is a powerful risk factor for diabetes, we examined the relations of fat (including type), fiber, sucrose, and other components of diet to risk of diabetes, among women with BMIs (in kg/m2) less than 29 kg/m2. After controlling for body mass index, previous weight change, and alcohol intake, we observed no associations between intakes of energy, protein, sucrose, carbohydrate, or fiber and risk of diabetes. Compared with women in the lowest quintile of energy-adjusted intake, and relative risks (and tests for trend) for those in the highest quintile were 0.61 (P trend = 0.03) for vegetable fat, 0.62 (P trend = 0.008) for potassium, 0.70 (P trend = 0.005) for calcium, and 0.68 (P trend = 0.02) for magnesium. These inverse associations were attenuated among obese women (BMIs greater than or equal to 29).