Abstract Background Although the Dietary Approaches to Stop Hypertension (DASH) diet is an accepted nonpharmacologic treatment for hypertension, little is known about what patient characteristics affect dietary adherence and what level of adherence is needed to reduce blood pressure (BP). Objective Our aim was to determine what factors predict dietary adherence and the extent to which dietary adherence is necessary to produce clinically meaningful BP reductions. Design Ancillary study of the ENCORE (Exercise and Nutrition Interventions for Cardiovascular Health) trial—a 16-week randomized clinical trial of diet and exercise. Participants/setting Participants included 144 sedentary, overweight, or obese adults (body mass index 25 to 39.9) with high BP (systolic 130 to 159 mm Hg and/or diastolic 85 to 99 mm Hg). Intervention Patients were randomized to one of three groups: DASH diet alone, DASH diet plus weight management, and Usual Diet Controls. Main outcomes measures Our primary outcomes were a composite index of adherence to the DASH diet and clinic BP. Statistical analyses performed General linear models were used to compare treatment groups on post-treatment adherence to the DASH diet. Linear regression was used to examine potential predictors of post-treatment DASH adherence. Analysis of covariance was used to examine the relation of adherence to the DASH diet and BP. Results Participants in the DASH diet plus weight management (16.1 systolic BP [SBP]; 95% CI 13.0 to 19.2 mm Hg and 9.9 diastolic BP [DBP]; 95% CI 8.1 to 11.6 mm Hg) and DASH diet alone (11.2 SBP; 95% CI 8.1 to 14.3 mm Hg and 7.5 DBP; 95% CI 5.8 to 9.3 mm Hg) groups showed significant reductions in BP in comparison with Usual Diet Controls participants (3.4 SBP; 95% CI 0.4 to 6.4 mm Hg and DBP 3.8; 95% CI 2.2 to 5.5 mm Hg). Greater post-treatment consumption of DASH foods was noted in both the DASH diet alone (mean=6.20; 95% CI 5.83 to 6.57) and DASH diet plus weight management groups (mean=6.23; 95% CI 5.88 to 6.59) compared with Usual Diet Controls (mean=3.66; 95% CI 3.30 to 4.01; P<0.0001), and greater adherence to the DASH diet was associated with larger reductions in clinic SBP and DBP (P≤0.01). Only ethnicity predicted dietary adherence, with African Americans less adherent to the DASH diet compared with whites (4.68; 95% CI 4.34 to 5.03 vs 5.83; 95% CI 5.50 to 6.11; P<0.001). Conclusions Greater adherence to the DASH diet was associated with larger BP reductions independent of weight loss. African Americans were less likely to be adherent to the DASH dietary eating plan compared with whites, suggesting that culturally sensitive dietary strategies might be needed to improve adherence to the DASH diet.