The incidence of meningococcal infections undergoes secular variations with modifications in the distribution of identified serotypes. Rhinopharyngeal carriage of meningococci, common in the community, is the natural means of immunization. Prevalence of this carriage varies across age groups and communities, as well as according to whether or not cases are present in the community under study. Identified factors that promote transmission of the bacteria include crowded living conditions, poor socioeconomic conditions, and, more controversially, respiratory tract viral infections. Development of meningococcal infection usually occurs within seven days of onset of carriage. Secondary cases account for approximately 3% of meningococcal infections in France. The risk of development of secondary cases is increased in subjects sharing the patient's home or exposed to his or her rhinopharyngeal secretions. Prevention of these secondary cases rests on chemoprophylaxis and immunization. The qualities of antimicrobial agents proposed for chemoprophylaxis are discussed, with special emphasis on spiramycin and rifampin which are the most widely used. This study, which rests on French epidemiologic surveillance findings and data from a review of the literature, forms the basis for new French guidelines.