Diuretics are an integral part of the management of symptomatic heart failure. Although they have been used for several decades, there is still some ambiguity and confusion regarding the outcome and the optimal way of using these common agents. There are no large-scale randomized controlled trials that have evaluated the effect of diuretics on mortality and long-term morbidity in diastolic and systolic dysfunction. Nonetheless, in short-term studies furosemide has demonstrated to reduce symptomatic congestive heart failure and hospitalization, and to improve exercise capacity in the setting of systolic dysfunction. In this review, the classes, sites of action and renal effect of diuretics are reviewed and the various indications, optimal doses and recommendations on effective use and disuse are discussed. Namely, this review addresses the effects of emerging diuretic agents such as eplerenone--a selective mineral corticoid receptor antagonist, nesiritide--a brain natriuretic peptide-recombinant, and conivaptan--a vasopressin antagonist, in attempt to provide an update on current knowledge, even though adequate clinic data are not available for all agents.