Loop diuretics are strongly recommended by current guidelines for the treatment of acute heart failure. Intravenous furosemide can be administered either as a continuous infusion or as an intermittent bolus. The choice between these two routes is not always obvious in clinical practice. The understanding of their different mechanisms of action, as well as the notion of diuretic resistance, can help identify patients who may benefit from either of these two routes. This article aims at discussing these aspects and their pathophysiology, as well as summarizing the current body of evidence from randomized trials comparing continuous vs. intermittent administration of furosemide in acute heart failure.