There are multiple classifications of status epilepticus (SE), each with unique clinical and electrical characteristics that evolve with continued seizure activity. This chapter focuses on non-convulsive SE (NCSE) as seen in the comatose patient in the intensive care unit (ICU) as well as generalized convulsive SE (GCSE), including its typical clinical evolution into subtle convulsive SE. There are multiple ways to classify SE based on the electrophysiological characteristics and clinical manifestations of seizure activity. The aetiology is the most significant prognostic indicator of SE and thus this classification is of particular clinical importance. The characteristic clinical features of GCSE initially include bilaterally symmetric tonic and/or clonic movements that are continuous but wane over time in an unconscious patient. Convulsive status epilepticus is a medical emergency that warrants aggressive and early treatment using a rationally based protocol that takes into account the clinical stage of SE.