Despite the use of increasingly potent antibiotics and aggressive cardiovascular monitoring and support, Gram-negative bacteremia and ensuing sepsis and septic shock remain a leading cause of morbidity and mortality after surgery and in critically ill patients. In previous years several new agents and techniques have been developed to improve management and outcome of severe Gram-negative infections. A recently introduced treatment is passive immunotherapy by administration of poly- or monoclonal anti-endotoxin antibodies. The current view--sustained by experimental and human studies--on the mechanism of protection afforded by immunotherapy is that the harmful effects of endotoxin are neutralized by cross-reactive antibodies to the core glycolipid structure of rough mutant Gram-negative bacilli. Two recent large clinical trials reported impressive results achieved through the use of monoclonal anti-endotoxin antibodies in certain subgroups of patients with Gram-negative sepsis. However, this treatment is empirical, expensive and it does not affect overall sepsis mortality. Cytokines such as tumor necrosis factor alpha and interleukin-1 play a pivotal role in sepsis. Experimental studies suggest that specific antagonism of these mediators might offer great perspectives for the treatment of Gram-negative sepsis. An early multi-pharmacological approach aimed at interruption of multiple steps underlying the inflammatory septic cascade will probably constitute the most promising future treatment of severe Gram-negative infectious disease.