The safety, tolerability, and hemodynamic effects of carvedilol in patients with heart failure were first studied in the mid 1990s. Positive results in these early trials led to 5 prospective, randomized, double-blind, placebo-controlled trials-the Australia/New Zealand Heart Failure Collaborative Group (ANZ) study and the 4 component studies of the US Carvedilol Heart Failure Trials Program. These studies were conducted to determine the clinical impact of long-term carvedilol therapy. Findings from these trials showed that carvedilol is a powerful therapy (1) in patients with chronic heart failure caused by left ventricular (LV) systolic dysfunction, improving morbidity and mortality; and (2) in patients with symptomatic heart failure, improving LV ejection fraction, improving clinical status, and slowing disease progression, resulting in reduction of the combined risk of hospitalization and mortality. This article discusses the design, results, and clinical implications of these trials.