In an attempt to ascertain the effects on blood pressure of variations in the dietary intake of sodium and linoleic acid, food preparation will be modified at two boarding high schools in New England over four school years. During the first year, dining hall food at one school will be prepared with 50% less sodium; the total intake of sodium by students (dining hall food, outside food, snacks) should be reduced by approximately 35%, to an average level of 75-90 mEq (less that 5 grams of salt) per day. The other school will serve as a control, continuing to prepare food with usual amounts of sodium. During the second year, the intervention will take place at the second school, wh le the other serves as a control. During the third and fouth years, sodium intake will be kept at usual levels while changes are made in food preparation alternately at each school to bring about a doubling in the polyunsaturated fatty acid intake of students (from 4% to 8% of dietary calories). Repeated food diaries, duplicate food samples and 24 hour urine collections by approximately 200 students at each school (those taking the basic course in Biology) will be utilized to monitor the dietary modifications and student compliance with the prescribed changes. The effects of these dietary changes on blood pressure will be monitored with weekly blood pressure masurements by the 200 students taking Biology at each school. An automatic blood pressure apparatus which has been found to give reliable measurements in this setting will be utilized. The effects of the dietary interventions on blood pressure will be estimated from differences in blood pressure between the schools (intervention and control). Among factors which will be evaluated as potential modifiers of the effect are age, gender, baseline blood pressure level, family history of hypertension, ponderosity and the degree of compliance with the dietary change. Previous studies at these school have shown a high degree of enthusiasm and compliance by participating students. Furthermore, such work has demonstrated that the desired level of dietary change can be readily achieved. Thus, the proposed study offers the opportunity to determine the frequency with which young persons will lower their blood pressure given such modifications in sodium and linoleic acid intake, and the magnitude of such changes. It should provide valuable information regarding results that could be expected if the current dietary recommendations of the U.S. government are applied to populations of "normal" young people.