Large doses of phenytoin were administered on 159 occasions to 139 adult patients. Most patients had had more than three seizures or were in status epilepticus. Based on response to treatment, patients could be divided into two groups. Those with excellent response (recurrent seizures, 10%; mortality, 1%) included known epileptics with exacerbation of seizures (n = 75), atypical alcohol withdrawal (6), or miscellaneous conditions (17). Those with poor results (recurrent seizures, 57% mortality, 38%) included patients with anoxic or metabolic encephalopathy (14), stroke or other vascular disease (14), brain tumor (5), or trauma (5).