Myasthenia Gravis is a neuromuscular disorder manifested by increasing weakness and fatigability of voluntary muscles with exercise, and partial or complete restoration of function following rest or the administration of anticholinesterase drugs. The anesthesiologists may be called upon to assist in the diagnosis of myasthenis, in treating the patient by artificial ventilation during acute exacerbations, to anesthetise the patient for thymectomy or other surgery. Therefore, the anesthesiologists must be familiar with the diagnosis and treatment of myasthnia gravis to carry on the appropriate therapy. Two cases of anesthesia for thymectomy in myasthenia gravis without using muscle relaxants was experienced, and no respiratory problems were encountered postoperatively.