BACKGROUND: Food insecurity refers to limited or uncertain access to food resulting from inadequate financial resources. There is a clear association between food insecurity and obesity among women, but little is known about the relationship between food insecurity and type 2 diabetes. OBJECTIVE: To evaluate whether there is an independent association between food insecurity and diabetes. DESIGN: Cross-sectional analysis of the nationally representative, population-based National Health and Nutrition Examination Survey (1999-2002 waves). PARTICIPANTS: Four thousand four hundred twenty-three adults > 20 years of age with household incomes < or = 300% of the federal poverty level. MEASUREMENTS: We categorized respondents as food secure, mildly food insecure, or severely food insecure using a well-validated food insecurity scale. Diabetes was determined by self-report or a fasting serum glucose > or = 126 mg/dl. RESULTS: Diabetes prevalence in the food secure, mildly food insecure, and severely food insecure categories was 11.7%, 10.0%, and 16.1%. After adjusting for sociodemographic factors and physical activity level, participants with severe food insecurity were more likely to have diabetes than those without food insecurity (adjusted odds ratio [AOR] 2.1, 95% CI 1.1-4.0, p = .02). This association persisted after further adjusting for body mass index (AOR 2.2, 95% CI 1.2-3.9, p = .01). CONCLUSIONS: Food insecurity may act as a risk factor for diabetes. Among adults with food insecurity, increased consumption of inexpensive food alternatives, which are often calorically dense and nutritionally poor, may play a role in this relationship. Future work should address how primary care clinicians can most effectively assist patients with food insecurity to make healthy dietary changes.