Studies among a total of about 300 patients with congestive heart failure treated over eight to ten months reveal a distinct and sustained benefit from vasodilator therapy. Increased longevity has not yet been established, but in most circumstances there has been noticeable symptomatic, radiological, and hemodynamic improvement. Unresolved problems continue to center around variability in response, difficulties in objective assessment (invasive and noninvasive) before and during therapy, and selection criteria for patients and drugs. Lesser problems include the construction of effective dosage schedules, deleterious effects after sudden withdrawal, development of tolerance, and side effects.