The Trial of Antihypertensive Intervention and Management evaluated nine diet-drug combinations in 878 mildly hypertensive, moderately obese participants using a 3 x 3 factorial design. Drugs evaluated were placebo, diuretic (chlorthalidone), and beta-blocker (atenolol); diets were usual (no intervention), weight reduction, and low sodium/high potassium (Na/K). This article reports 6-month dietary changes and the effect of dietary change on blood pressure. Six-month mean weight change was -4.7 kg in the weight reduction group, -0.3 kg in the Na/K group, and -0.5 kg in the usual-diet group. At 6 months, daily electrolyte excretion had changed in the Na/K intervention group. Daily sodium excretion decreased from 138.0 to 112.0 mmol in the Na/K group and increased from 134.1 to 138.4 mmol in the weight reduction group and from 129.1 to 137.0 mmol in the usual-diet group. Daily potassium output increased from 58.7 to 71.4 mmol in the Na/K group, from 57.0 to 60.5 mmol in the weight reduction group, and from 55.3 to 59.1 mmol in the usual diet group. Analysis of 3-day food records indicated that sodium intake decreased from 141.1 to 85.8 mmol and potassium intake increased from 76.4 to 90.5 mmol. Our results indicate that the goal for weight reduction was more easily achieved than the goal for electrolyte modification.