EEG is a major tool in convulsive status epilepticus. Several techniques may be used, including conventional or digitized EEG using 4, 8, 10 or 16 channels, continuous monitoring with or without simultaneous video recording, and cerebral function monitor. During the first phase, in the emergency ward, EEG may be useful in severe convulsive status epilepticus to assess further evolution and/or prognosis. However, rapid control of seizure at this phase is the primary goal, and optimization of EEG availabilities may lead to more systematic indications. After adequate control of seizures, EEG is mandatory in the following situations: i) a difficult-to-control convulsive status epilepticus, with a high risk of subsequent evolution towards subtle status epilepticus; ii) a resistant status epilepticus which needed high dose of sedatives drugs and/or curarization, to evaluate the level of anaesthesia and to watch for recurrence of epileptiform abnormalities; iii) a permanent, unexplained impairment of consciousness which followed an apparently successful treatment, to detect non convulsive status epilepticus; 4. a doubtful clinical diagnosis, to confirm pseudo-status epilepticus.