Status epilepticus (SE) is a common diagnosis in critically ill patients that may bear significant morbidity and mortality. Nowadays it is defined as continuous seizure activity lasting for more than 5 mins and requiring a specific treatment. A generalised convulsive state is a medical emergency burdened by high mortality, especially in the elderly, because repeated seizures swiftly induce significant metabolic and cardiocirculatory derangement. Two different kinds of SE are commonly recognised, depending on the presence of convulsion: convulsive SE and non-convulsive SE, which have different electroencephalographic patterns and require different therapies. In this review we provide an overview of this intriguing issue, focussing on critically ill patients.