The most important indications for passive immunotherapy in the field of infectious diseases are reviewed. Intramuscular immunoglobulins are useful in prophylaxis and treatment of diseases due to bacterial exotoxins and in prophylaxis of some viral infections. However, their efficacy against bacterial infections has not been demonstrated. Intravenous immunoglobulins have theoretical advantages in these infections. The few clinical studies performed in neonates and in patients of surgical intensive care units have suggested modest benefits. However, these studies did not allow to decide whether intravenous immunoglobulins have a role in these situations. Another approach still under investigation is to administer polyclonal antibodies directed against the central part of the endotoxin, the structure of which is well preserved among gram-negative bacteria. These antibodies have improved the survival of patients with gram-negative bacteremia or septic shock. When given prophylactically, they have reduced the incidence of gram-negative shock and related mortality in patients from surgical intensive care units. Further studies are in progress to determine the class and the precise specificity of these protective antibodies.