During the past decade a number of drugs have been developed for the specific purpose of reducing blood pressure in hypertensive patients. Attempts to evaluate these agents definitively have been hindered either by lack of suitable controls, failure to eliminate bias, or by insufficient numbers of patients. Inevitably, under such circumstances, differences of opinion have arisen as to the relative effectiveness, tolerability, and safety of the various antihypertensive agents now in general clinical use. Furthermore, well-controlled data have been lacking on the value of blood pressure reduction in preventing or delaying cardiovascular-renal damage in hypertensive disease of mild and moderate severity.
In view of the obvious importance of the problem it was decided to institute a program which would permit more reliable comparisons of the therapeutic effectiveness of antihypertensive agents. A cooperative investigation was best suited for the purpose, since it encompasses a sufficiently large series of patients to permit