The Studies of Left Ventricular Dysfunction (SOLVD) is an extensive program of research that has 3 components. (1) Two large double-blind randomized trials evaluate the effects of enalapril on mortality, morbidity and quality of life of patients with left ventricular (LV) dysfunction with overt congestive heart failure (CHF) (Treatment Trial in 2,500 patients) and without overt CHF (Prevention Trial in 4,600 patients). (2) Seven detailed sub-studies evaluate the effect of enalapril on a number of intermediate outcomes such as right and LV function and hemodynamics, LV mass and wall stress, hormones, arrhythmias, exercise capacity and quality of life in subsets of patients in the 2 large trials. (3) Finally, a registry of 6,336 patients with congestive heart failure or LV dysfunction is designed to describe the clinical course of an unselected group of patients. The rationale and design of a tiered approach to clinical trials that are large enough to provide reliable information on mortality and morbidity, yet provide relevant information on other endpoints, are described.