Critically ill patients experience seizures frequently regardless of whether they have underlying medical illnesses or have undergone a surgical procedure. Many medical and surgical complications increase the likelihood of seizures including hypoxia, cerebral ischemia, medications, drug withdrawal, infection, surgical injury, and metabolic derangements. Most seizures in the ICU occur in patients without prior history of seizures. In fact it has been reported that neurologic complications occur in about 12% of patients admitted to the ICU without prior intracranial pathology, and of these, 28% experience seizures. About 90% of seizures in the ICU are generalized tonic-clonic. However, about 10% of patients will have complex-partial or other non-convulsive seizures including non-convulsive status epilepticus (i.e., ongoing electrical seizures lasting more than 5 minutes). Patients with non-convulsive seizures represent a difficult dilemma for intensivists. It has been estimated that the incidence of non-convulsive status epilepticus may be 5% to 50% in patients in coma and the incidence of non-convulsive seizures in general could be as high as 34%. The key point to learn from these data is that without monitoring (e.g., electroencephalography [EEG]), the diagnosis of non-convulsive seizures and status epilepticus will be missed, to the detriment of the patient.