This chapter outlines the clinical features of the status epilepticus (SE) in the most important of the uncommon causes, while listing the others. Paraneoplastic conditions such as paraneoplastic limbic encephalitis may present with focal motor or non-convulsive SE, and on rare occasions, may have multiple semiologies. The seizures and SE may be due to an opportunistic infection, HIV encephalitis, associated central nervous system (CNS) lymphoma or other complications, metabolic disturbance, or drug treatment. Ring chromosome 20 typically presents with non-convulsive SE and has a characteristic electroencephalogram (EEG) pattern. A total of 181 different etiologies causing SE were identified in the literature search, and of these most can be diagnosed by magnetic resonance imaging (MRI), or by serological (infectious or inflammatory causes), biochemical (metabolic and toxic causes), genetic, biopsy, or other clinical investigations. Treatment of the SE itself is often with conventional antiepileptic drug (AED) therapy.