Previous work in the study measured the effects on blood pressures of variations in the dietary intake of sodium and linoleic acid in adolescents at the two New England boarding schools of Phillips Exeter Academy and Phillips Andover Academy. During the first year, dining room food at one school was prepared with 50 percent less sodium; total intake of sodium by students including dining hall food, outside food and snacks was reduced by approximately 35 percent. The other school served as the control. During the second year, the intervention took place at the second school. During the third and fourth years, sodium intake was kept at usual levels while changes were made in food preparation to double the polyunsaturated fatty acid intake from four percent to eight percent of dietary calories. Food diaries, duplicate food samples, and 24-hour urine collections by approximately 200 students at each school were used to monitor dietary modification and student compliance. Weekly blood pressure measurements were performed on the 200 students at each school.