Lorazepam was compared with diazepam for the treatment of status epilepticus in a double-blind, randomized trial. Seventy-eight patients with 81 episodes were enrolled. Patients received one or two doses of either 4 mg of lorazepam or 10 mg of diazepam intravenously. Seizures were controlled in 89% of the episodes treated with lorazepam and in 76% treated with diazepam. The times for onset of action of the medications did not differ significantly. Adverse effects occurred in 13% of the lorazepam-treated patients and in 12% of the diazepam-treated patients. Respiratory depression and arrest, the most frequent adverse effects, were treated symptomatically; no adverse sequelae were noted.