Diazepam (Valium) was administered intravenously to 26 patients with varying degrees of prolonged, uncontrolled seizure activity. The seizures were terminated rapidly in 16 cases and less satisfactorily in 10. Patients with acute, rapidly progressive cerebral disorders were most resistant to treatment. Concurrent electroencephalographic monitoring demonstrated in 13 of 18 tracings that diazepam quickly suppressed the spikes. Intramuscularly administered follow-up doses of diazepam, used with other anticonvulsants, assisted in the maintenance of control. Intravenously administered diazepam is an excellent short-term anticonvulsant with relatively few adverse reactions. It is often effective after large doses of other parenterally administered anticonvulsants have failed to establish seizure control.