BACKGROUND: To know the incidence, clinical presentation, differential diagnosis and resistance level to antibiotics in pediatric meningitis. METHODS: 173 cases of meningitis (bacterial: 69, viral: 104) have been prospectively followed during 1988 according to a previously established clinical and laboratory protocol. RESULTS: Meningitis attack rate was 60 cases/100,000 children younger than 15 years per year (meningococcal: 25/100,000, Haemophilus: 2/100,000). Mortality was 1.4%. 40% of bacterial meningitis received previous antibiotic treatment. Sensitivity of culture, Gram stain, and direct antigen detection by latex and EIA was 79%, 61.7%, 20.5% and 34%, respectively. Bacterial and viral differential diagnosis, by the application of Boyer's score was 95% sensitive and 98% specific. Four out of six cases of Haemophilus meningitis were ampicillin and chloramphenicol resistant; 39% of meningococcus had their penicillin susceptibility decreased between 2 and 8 times, although no therapeutic failures were seen. CONCLUSIONS: Laboratory parameters might not separate bacterial and viral meningitis at early stages of illness. Gram stain is an excellent and sensitive method of bacterial detection in CSF. Moderate resistance to penicillin in meningococcus is very frequent but clinical failures are not yet present.