Abstract Body: Background: People with type 2 diabetes (T2D) and hypertension are at high risk for cardiovascular events, and a minority achieve recommended blood pressure (BP) goals. While trials have established the benefits of antihypertensive drug therapy in T2D, few studies have tested the BP-lowering effects of diet, and there is a need to optimize BP-lowering diets for people with T2D. Here, we report the main findings of the Dietary Approaches to Stop Hypertension for Diabetes (DASH4D) trial, a randomized crossover feeding study that tested the effects of the DASH4D diet and dietary sodium reduction on BP in adults with T2D. Methods: The DASH4D diet was developed by our multidisciplinary team, optimizing the original DASH diet for T2D by including lower carbohydrate content, higher unsaturated fat, and lower potassium for safety with kidney disease. Major inclusion criteria were age ≥18 years, T2D, systolic blood pressure (SBP) 120-159 mmHg, and diastolic blood pressure (DBP) <100 mmHg. Participants were randomized to a sequence of four diets, each for five weeks: 1) DASH4D diet with lower sodium, 2) DASH4D diet with higher sodium, 3) comparison (typical American) diet with lower sodium, and 4) comparison diet with higher sodium. Participants were provided all of their food, prepared in the study metabolic kitchen, and ate no outside food. Weight was held constant. The primary and secondary outcomes were end-of-period SBP and DBP, respectively. The primary dietary contrast compared the effects of the DASH4D diet with lower sodium vs. comparison diet with higher sodium using linear mixed effects regression with a modified intention-to-treat approach. Results: Of 102 participants, 85 completed all four diet periods. Mean age was 66 years, 66% were women, 88% were non-Hispanic Black, mean baseline BP was 135/75 mmHg, and 66% used ≥2 antihypertensive medications. Compared to the comparison diet with higher sodium, the DASH4D diet with lower sodium reduced end-of-period SBP (mean Δ -4.5 mmHg, 95% CI: -7.1 to -1.9, p<0.001) and DBP (mean Δ -2.2 mmHg, 95% CI -3.6 to -0.8). The majority of SBP reduction occurred in the first 3 weeks of each diet, and the effect of sodium reduction appeared stronger than the effect of the DASH4D diet (Figure). Adverse events were infrequent on all diets. Conclusions: In adults with T2D, most treated with multiple antihypertensive medications, the DASH4D diet combined with sodium reduction achieved a clinically significant reduction in BP.