Non-convulsive status epilepticus is an insidious condition and a challenging diagnosis for neurologists on call. The condition must, however, be recognized, since it constitutes a neurological emergency. Non-convulsive status epilepticus may also be associated as an additional complication with an acute neurologic disease, in which case an EEG recording is usually required. In addition, non-convulsive status epilepticus can be found in a significant proportion of patients with unconsciousness of unknown origin.