Neuromuscular disorders are important causes of prolonged morbidity in intensive care unit. Specific disorders facing the neurologist in the intensive care unit may have been present before admission to the unit or develop as a secondary complication of their stay. A bedside neurological examination, followed by electrophysiological testing, including testing of the respiratory system, is crucial in providing the neuromuscular diagnosis. Among the neuromuscular disorders that confront the clinician in the unit are motor neuron disease, acute polyneuropathies including acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome) and critical illness polyneuropathy, neuromuscular transmission disorders including myasthenia gravis, and specific myopathies. This chapter reviews the differential diagnosis and the unique features of neuromuscular conditions that may complicate critical illness and admission to the intensive care unit.