Pimobendan, an inhibitor of phosphodiesterase III, is an inotropic, vasodilating drug that has a sensitising effect on calcium channels. It is usually prescribed for the treatment of chronic heart failure. The objective of this study was to determine the effects of using a new injectable formulation of pimobendan in the treatment of hyperacute and severe congestive heart failure in dogs. This is a descriptive clinical study performed in three dogs with heart disease assessed during acute congestive heart failure and after diuretic therapy in combination with intravenous pimobendan. The use of intravenous pimobendan in association with diuretic therapy in the acute phase of congestive heart failure resulted in improvements of haemodynamic parameters and clinical signs in the three patients included in the study.