Objective: To study the clinical therapeutic characteristics of myasthenia gravis (MG) with hyperthyroidism and the effects of surgical procedures for the patients. Methods:Subtotal thyroidectomy,thymectomy,and simultaneous subtotal thyroidectomy and thymectomywere performed on eleven patients with MG and hyperthyroidism. These patients were followedup after the operation. Results :The neck incisions were infected in two of seven type Ⅱ b patientsdue to trachestomy and the infected incisions were surgically healed. The MG symptoms of threecases (1 cases in type Ⅱ. and 2 cases in type Ⅱ b) relapsed in 3 to 6 months after subtotal thy-roidectomy. The MG symptoms of 2 cases (1 case in type Ⅱa and 1 case in type Ⅱ b) relapsed in 8to 12 months after thymectomy. Among six patients treated by simultaneous subtotal thyroidecto-my and thymectomy,the MG symptoms relapsed in a type I case 3 months after the operation,remitted in three case (1 case in type Ⅱ, and 2 cases in type Ⅱb) and improved in two type Ⅱ bcases since the operations. Conclusion:The simultaneous subtotal thymectomy and thyroidectomyfor patients with MG and hyperthyroidism might have better effects,although infective opportuni-ty of the neck incisions increased owing to trachestomy. However,the prognostic effects were notvery satisfactory whether simple subtotal thyroidectomy or thymectomy for the patients with MGand hyperthyroidism was performed.