From 1984 to 1990, six patients with histologically and endocrinologically proven ectopic ACTH syndrome were treated in our department. The lesion in five patients was clinically evident, but in the other was occult. All lesions were located within the chest. Four were thymic carcinoid and the other two were bronchial carcinoids. Most of the patients had typical clinical manifestations of Cushing's syndrome. Laboratory tests including histopathological examination confirmed the diagnosis of ectopic ACTH syndrome. The treatment consisted of surgical removal of the mass supplemented by radiotherapy. The results showed that after treatment all patients had satisfactory remission. Two bronchial carcinoid patients have been living for 40 and 88 months respectively without recurrence. Among 4 thymic carcinoid patients, only one has been living with no tumor for 34 months. One patient had recurrence and the other 2 died 32 and 50 months after the treatment respectively. However, the symptoms of two thymic carcinoid patients had not been relieved at all until radiotherapy was given. This paper discusses the method, dose and indications of radiotherapy. It should be pointed out that the prognosis of bronchial carcinoids is good while that of thymic carcinoids is relatively poor.