After prompt diagnosis, severe myasthenia gravis and Guillain-Barré syndrome (GBS) usually require management in the intensive care unit. In the myasthenic patient, recognition of precipitating factors is paramount, and frequent monitoring of bulbar, upper airway, and/or respiratory muscle strength is needed to identify impending myasthenic crisis. Noninvasive ventilation can be attempted prior to intubation and mechanical ventilation in the setting of respiratory failure. Cholinesterase inhibitors should be discontinued, but resumed prior to extubation, and steroid dosage could be increased once the airway is secured. In GBS, hemodynamic and respiratory monitoring are essential; however, respiratory failure can develop rapidly and intubation with mechanical ventilation is often required and can be prolonged. Guillain-Barré syndrome can also be complicated by dysautonomia necessitating specific therapies. Prompt recognition and initiation of immunotherapy including intravenous immunoglobulin or plasmapheresis, together with supportive care including treatment of underlying infections and physical therapy, can improve outcomes in both myasthenic crisis and GBS.