Myasthenia gravis is an autoimmune disease of the skeletal muscles that improves with rest and is characterized by weakness and fatigue. A critical condition requiring mechanical ventilation, known as myasthenic crisis, may occur due to infections arising in the course of the disease, variations in drug doses, surgery, stress and pregnancy. A patient brought to the emergency ward with respiratory distress had been under long-term follow-up for chronic obstructive pulmonary disease, and myasthenia gravis for the preceding 3 months. Acute excacerbation of chronic obstructive pulmonary disease was suspected, and the patient was intubated and transferred to intensive care unit. Due to prolonged respiratory insufficiency, myasthenic crisis was suspected. Following intravenous immunoglobulin treatment for six days, the patient was successfully weaned from the mechanical ventilator. Myasthenic crisis should be considered in patients requiring mechanical ventilation due to respiratory insufficiency and with a history of myasthenia gravis. We think that rapid elimination of the causes triggering the crisis, close monitoring and treatment will obviate the need for mecha- nical ventilation