A retrospective study was performed on 98 patients with myasthenia gravis diagnosed at the Department of Rehabilitation Medicine, Gospel Hospital, Kosin University and Department of Rehabilitation Medicine, College of Medicine, Hanyang University from January 1988 to December 1995.

The purpose of this study was to examine the findings of EMG and Tensilon test according to the clinical pictures of myasthenia gravis and to determine correlation and reliability of EMG and Tensilon test.

Women were affected more frequently than men, with a ratio of 1.8:1 and there were peaks of incidence in their 3rd and 4th decades. According to modified Osserman's classification, group I was 26 patients, group IIa was 36 patients, most common, group IIb was 15 patients, group III was 15 patients and group IV was 6 patients. Thymoma was found in 22 patients(22.4%), and thymectomy was performed in 12 patients among them.

In Tensilon test, performed in 74 patients, 64 patients(86.5%) revealed positive response and in EMG test, performed in 51 patients, 36 patients(70.6%) revealed positive response. 36 patients were performed both Tensilon test and EMG test and 33 patients(91.7%) revealed positive response on either Tensilon or EMG test.

On the basis of this study, it is necessary to perform both EMG and Tensilon test for diagnosis of myasthenia gravis.