DASH, a randomized, multicenter, controlled trial, compared the effects of three dietary patterns on blood pressure. The study design consisted of a three-week run-in period during which eligible participants were provided a diet that approximated a typical American diet in nutrient content. After run-in, eligible participants were randomized to one of three dietary patterns which lasted for eight weeks: a 'typical' American diet in which the macronutrient and fiber content reflected current United States consumption and was relatively low in calcium, potassium, and magnesium; a diet that was high in fruits and vegetables, and therefore high in potassium, magnesium, and fiber. The macronutrient and calcium content of this diet otherwise resembled that of the typical American diet. The third diet, termed the DASH diet, was high in fruits, vegetables, and low-fat dairy products, and had a favorable macronutrient profile. This diet was low in saturated fat, total fat, and cholesterol, was moderately high in protein, and had a high content of calcium, potassium, magnesium, and fiber. All three diets had about 3 grams of sodium daily--slightly below the average U.S. consumption-- and all included fresh, frozen, canned, and dried foods. None of the diets was vegetarian or used specialty foods containing fat substitutes. Alcohol and caffeine-containing beverages were limited and monitored. Because it was important that good compliance to the diet be assured, food was provided to the free-living study participants. The primary endpoint was change in diastolic blood pressure from baseline to the end of the study. The study compared the changes in diastolic blood pressure among the three dietary patterns. Screening began in June 1994. Randomization began in September 1994 and was expected to take two years. Support for the trial ended in July 1997.