Meningococcal disease is an infection caused by Neisseria meningitidis, a gram-negative diplococcus that is the leading cause of bacterial meningitis in children and young adults in the United States, with an estimated 2,600 cases reported each year. N. meningitidis infection rates are highest in children 3 to 12 months of age. Four distinct clinical situations are associated with meningococcal infection. The most common is asymptomatic nasopharyngeal colonization. Benign bacteremia is discovered in the absence of classical clinical findings of meningococcemia, but blood cultures are positive for N. meningitidis. Meningitis, the most common pathologic presentation, is associated with fever, headache, and nuchal rigidity. The mortality rate is about 5% in children and 10% to 15% in adults. Meningococcemia, the most severe form of infection, may involve petechial rash, hypotension, and disseminated intravascular coagulation. It is a fulminant condition that can, if untreated, progress from initial symptoms to coma and death in 12 to 48 hours. Spread of these endemic cases can be controlled by administering prophylactic antibiotics to close contacts of patients.