Levosimendan is one of the first agents of a new class of drugs known as calcium sensitizers. These drugs are believed to increase cardiac contractility by sensitizing cardiac myofibrils to calcium, and may therefore be of clinical benefit in the treatment of low-cardiac output states, particularly congestive heart failure. In addition to sensitizing troponin to intracellular calcium, levosimendan has been shown to inhibit phosphodiesterase III, which may contribute to its positive inotropic effect, and open adenosine triphosphate (ATP)-sensitive potassium channels (K(ATP)), which may produce vasodilation. Unlike currently available intravenous inotropes, levosimendan does not increase myocardial oxygen utilization, has not been shown to be proarrhythmic, and has been used effectively in the presence of beta-blocking medications. Levosimendan also has not been shown to impair ventricular relaxation, which was an initial concern with this class of drugs. Clinical studies of levosimendan have demonstrated short-term hemodynamic benefits of levosimendan over both placebo and dobutamine. While large-scale, long-term morbidity and mortality data are scarce, the Levosimendan Infusion versus Dobutamine in severe low-output heart failure (LIDO) study suggested a mortality benefit of levosimendan over dobutamine up to 180 days after treatment. Clinical studies comparing levosimendan with other positive inotropes, namely milrinone, are lacking. Levosimendan treatment appears to be well-tolerated, with the primary adverse events being headache and hypotension. No clinically significant drug-drug interactions have been reported with levosimendan to date. The clinical future of levosimendan will depend on the results of larger, ongoing clinical trials.