The records of 187 patients with bacterial meningitis were reviewed. Seizures were a presenting manifestation in 25 (13%). Seven (28%) of the patients with a presenting seizure had been taking antibiotics prior to the diagnosis. Four of seven pretreated patients did not have additional signs or symptoms with the seizure, while all 18 patients without treatment had additional findings (P less than 0.01). Patients developing seizures while hospitalized had a poorer outcome than those without seizures. Patients with bacterial meningitis may present with only a seizure if they have been taking oral antibiotics; therefore, all patients taking antibiotics who develop a seizure require a lumbar puncture to exclude meningitis.