A retrospective hospital chart review of meningococcal meningitis cases in Costa Rica revealed a large number of cases confirmed in the laboratory by Gram-stained smear and/or culture of spinal fluid. A large percentage of the isolates studied were serogroup C and all of these were sulfonamide resistant. The age-specific attack rates were high in the preschool children with the highest attack rate in children 3 to 5 months of age. Case fatality ratios were 14% overall, with the low fatality rates in individuals 10 to 29 years of age. The outbreak of serogroup C meningitis in 1970--1971 was relatively brief, country-wide, and not predominantly a urban outbreak. The few secondary cases observed occurred within the first 2 weeks of the primary case.