The primary objective of this multicenter cooperative clinical trial was to determine if dietary modification would enable drug controlled hypertensive patients to remain at 'goal blood pressures' after antihypertensive medication was withdrawn. The proposal made use of the HDFP hypertensive population who had five years of treatment for their hypertension. Additionally, the group of investigators proposed to determine if dietary treatment would permit patients not previously adequately controlled under the HDFP program to achieve normalization of blood pressure with a combination of dietary modification and drug treatment. The study also proposed to search for predictors (i.e., levels of hormonal agents such as plasma renin activity) of responsiveness to dietary manipulation among the hypertensive population as well as to identify psychological attributes that might be of importance in managing these patients.