13 children, 8 girls and 5 boys, aged 2-15 months (mean 8.5 months), with Haemophilus influenzae meningitis were treated with aztreonam. Aztreonam was administered intramuscularly in a dose of 50 mg/kg every 8 h. 10 of the infants were in coma and 3 were drowsy when first examined in hospital. All except 2 infants, who were in coma and who died within 24 h of starting therapy, recovered quickly. All patients became fully alert within 4-5 days and afebrile within 5 to 6 days.