Meningococcal septicemia and meningitis continue to be important causes of devastating illness, death, and long-term disability in both developed and resource-poor countries of the world. Few diseases have attracted as much public attention, or are as feared by parents and family members, as well as the medical staff who have to care for affected patients. The unexpected and unp- dictable occurrence of the disease in previously healthy children and young adults, its rapid progression, and the frequent occurrence of purpura fulminans with the resulting gangrene of limbs and digits and the requirement for mutilating s- gery, have all heightened both public and medical interest in the disease. Over the past two decades there has been a rapid increase in knowledge of many aspects of meningococcal disease as a result of intensive efforts by workers in many different fields: clinicians have studied the early presenting features and acute pathophysiology of the disorder; clinical scientists have explored the immunopathological mechanisms responsible for disease and have highlighted the important roles played by the host inflammatory response and pro-inflammatory cytokines in mediating damage to blood vessels and organs; microbiologists have developed new diagnostic methods; public health phy- cians and epidemiologists have improved surveillance techniques with the help of molecular tools provided by bacterial population biologists; and basic sci- tists have used the powerful new tools in molecular and cell biology to elucidate virulence mechanisms.