The possibilities for therapy in the field of severe cardiac insufficiency have been extended in recent years by the introduction of novel agents endowed with a positive inotropic action. These substances may be arranged in two large classes: sympathomimetic agents and "non sympathomimetic--non digitalis-like" inotropic agents. The stimulant action of noradrenaline, adrenaline and isoproterenol on beta-adrenergic myocardial receptors has been clearly demonstrated but the usefulness of these medicines is limited by their positive chronotropic and arrhythmogenic actions. Dopamine and dobutamine have proved to be very useful in the treatment of patients in intensive care units. However, the exclusively intravenous route of administration limits their importance to the medium or long term. Several compounds, which are active by the oral route, have been the subject of therapeutic trials for the short or medium term. The problems posed by their use result, in the first place, from an insufficient understanding of their mechanism of action. Some of them (pirbuterol, salbutamol, terbutaline, penoterol) seem to act preferentially on B2 adrenergic receptors and the haemodynamic effect results, in part or predominantly, from the vasodilator action which they cause. On the other hand, other agents (prenalterol, ICI 108-87) show a relative selectivity for B1 adrenergic receptors. Ibopamine exerts its action on B1 receptors and dopaminergic receptors. A second problem concerns the hypothetical character of their long term therapeutic activity. A major problem in the use of several of these sympathomimetic agents in chronic treatment is the appearance of a desensitization of the beta receptors.(ABSTRACT TRUNCATED AT 250 WORDS)