During an epidemic of meningococcal disease in Belo Horizonte, Brazil, a retrospective survey was carried out to assess the risk of meningitis associated with exposure in a schoolroom. Forty-seven of 17,012 students reportedly had meningitis in August-November 1974, an incidence of 276 per 100,000. Four of 1356 students with classroom exposure to a case contracted meningitis (secondary attack rate, 295 per 100,000). The results indicate that in the population surveyed, 95% of whom were from 7 to 14 years of age, there is no significantly increased risk associated with classroom exposure to a student with meningitis. Antibiotic prophylaxis of classroom contacts is therefore not indicated and should be reserved for contacts known to be at increased risk, such as members of the patient's household or those having direct contact with the patient's oral secretions.