OBJECTIVE - To examine the prospective association between accordance with the 2005 Dietary Guidelines for Americans (DGA) and subsequent diabetes incidence and changes in cardiometabolic risk factors. RESEARCH DESIGN AND METHODS - The sample consisted of 4,381 black and white young adults examined repeatedly from 1985 to 2005. We used the 2005 Diet Quality Index (DQI) to rate participants' diets based on meeting key dietary recommendations conveyed by the 2005 DGA. RESULTS - Overall, we found no association between DQI score and diabetes risk using Cox models adjusted for potential confounders. Higher DQI scores were associated with favorable changes in HDL cholesterol and blood pressure overall (P for trend <0.05), but with increased insulin resistance among blacks (P for trend <0.01). CONCLUSIONS - Our findings highlight the need for evaluation of the DGA's effectiveness, particularly among ethnic minority populations. Clinicians should be aware that following the DGA might not lower diabetes risk. © 2011 by the American Diabetes Association.