A multicenter, randomized, controlled, double-blind U.S. trial is comparing the combined effects of diet treatment and 1 of 5 active drug regimens with diet treatment alone, for the long-term management of middle-aged adults with "mild" hypertension. Factors stimulating this trial are (1) data documenting the high prevalence of mild hypertension in the adult population; (2) mild hypertension's responsibility for a high proportion of morbidity and mortality attributable to hypertension overall; (3) data from long-term hypertension intervention trials showing reduced morbidity and mortality of people with mild hypertension with use of either diuretics or β blockers as step-1 therapy, and other trials that failed to demonstrate beneficial impact on morbidity and mortality, possibly due to residual questions concerning aspects of benefit to risk ratios with these medications; (4) recent data from trials showing long-term control of mild hypertension and other risk factors by nutritional means; (5) lack of data from long-term trials on benefit to risk ratios with newer drugs such as selective α1 inhibitors, angiotensin converting enzyme inhibitors and calcium channel blockers; (6) paucity of data from trials on long-term combined effects of diet and drug therapy, and of diet alone, for people with mild hypertension. During the next few years, phase 1 of the trial will study 6 groups of drugs. The step-1 drugs are (1) angiotensin converting enzyme inhibitor (enalapril), (2) α1 inhibitor (doxazosin), (3) β blocker (acebutolol), (4) calcium channel blocker (amlodipine), (5) diuretic (chlorthalidone) and (6) placebo. All participants are to receive vigorous sustained nutritional counseling to reduce obesity, moderate sodium intake and avoid heavy use of alcohol. Key endpoints for phase 1 of the study are the need for additional medication to control mild hypertension, side effects (i.e., clinical and biochemical) and consequent need to discontinue drug and quality of life. Phase-1 data are to be used to complete the phase-2 design, with the ultimate aim to assess effects on morbidity and mortality.