There has been an intensive search for safe and clinically effective inotropic agents for use as adjunctive therapy in patients with advanced heart failure. Pimobendan is a benzimidazole-pyridazinone derivative with calcium-sensitizing properties that increases myocardial contractile force without increasing intracellular calcium. This review summarizes the data from five controlled, randomized prospective trials of pimobendan that demonstrate significant improvements in exercise capacity and quality of life in patients with heart failure. The clinical benefits of pimobendan found in these trials contrast with the adverse experience noted previously with milrinone and enoximone. This may be related to the different mechanism of action of pimobendan or to a study design that permitted examination of a lower dosage. These cumulative data suggest that pimobendan may have a useful adjunctive role in heart failure and that further assessment of its effects on overall mortality is needed.