Diuretics are frequently administered to relieve congestive symptoms in patients with heart failure (HF). Despite their widespread use, prospective data on the potential of diuretics to modulate HF-related morbidity and mortality are scarce. Diuretic efficacy may be limited by adverse neurohormonal activation and by "congestion-like" symptoms that may occur in the absence of fluid overload. Herein, we review the current knowledge on diuretic use and outcomes in HF.