Neisseria meningitidis is an aerobic, gram-negative diplococcus commonly found in the nasopharynx. Many healthy individuals are colonized with this bacterium, but it can cause serious, life-threatening disease. Humans are the only known reservoir, and transmission occurs through respiratory secretions. While there are at least 13 known meningococcal serogroups, 6 of them cause the majority of cases: A, B, C, X, Y, and W-135; four serogroups circulate in the United States (B, C, W, Y). Hyperendemic meningococcal diseases occurs in several areas of the world, especially sub-Saharan Africa. In the United States, most cases are sporadic, not outbreaks. However, outbreak-related cases have greater morbidity and mortality than sporadic cases. Patients with meningococcal disease should be promptly identified, and Droplet Precautions should be started when the diagnosis is initially suspected. Household contacts and individuals with direct exposure to patients’ respiratory secretions require the administration of postexposure antimicrobial prophylaxis. Various meningococcal vaccines are available; in the United States, they are recommended for populations at highest clinical or epidemiological risk of developing invasive meningococcal disease.