Abstract During the winter 1969 a small epidemic of meningococcal meningitis occurred in a naval training centre in Norway. After sulphonamide prophylaxis most of the meningococcal strains isolated from throat cultures from the recruits were resistant to sulphonamides (8, 9). Serological studies were undertaken in 43 of the recruits, of whom 72% were found to be carriers of meningococci on at least one occasion. All these isolated strains were resistant to sulphonamides. In paired serum specimens, taken at the beginning of the epidemic and 6 weeks later, no increase in bactericidal antibodies against 4 meningococcal test strains belonging to the serogroups A, B, C, and Y was demonstrated. Against meningococcal strains isolated from the recruits themselves, however, a significant rise in titre was found, indicating that the recruits had been infected at about the same time as the first serum specimen was taken. In 26 members of the permanent staff, 2 of them carriers of meningococci, the bactericidal titres were about equal to those in the recruits. Thus, the lower carrier rate in the permanent staff does not seem to be due to increased bactericidal potency of the serum.