Pharmacologic blockade of beta-adrenergic receptors is a frequent therapeutic intervention in critically ill patients. Today's strategies predominantly include the treatment of cardiovascular diseases like hypertension and cardiac arrhythmias. Furthermore, beta-adrenergic antagonists are routinely used to prevent the catecholamine-induced hypermetabolism in critically ill patients suffering from severe burn injury. In addition to these well known beneficial effects of beta-adrenoceptor blocking agents it has been demonstrated, that the adrenergic system is involved in the modulation of cellular immune functions. Therefore, the immunomodulatory properties of beta-adrenergic antagonists have been established during the last years and the scientific focus was addressed on the proposed immunologic side effects of a beta-adrenergic blockade and its potential effect on the clinical course of critical illness. This manuscript reviews the rational and the effect of the therapeutic use of beta-adrenergic antagonists in critically ill patients on the base of the current literature and further emphasizes on potential immunologic side effects.