From SEP. 1979, 137 cases of myasthenia gravis under the clinical impression at Seoul National University Hospital were analysed by repetitive supramaximal stimulation EMG study.

The results obtained were as follows:

1) Among the 137 cases, 66 cases(48.2%) were positive but 59 cases(43.1%) were negative.

2) The most peak age incidence was the third decade(25.8%) in female.

3) In repetitive supramaximal stimulation test, positive rate in proximal muscles was higher than distal muscles: 92% in proximal muscles, 76% in distal muscles.

4) The slow repetitive supramaximal stimulation was more sensitive than fast repetitive supramaximal stimulation: The decremental ratio of slow and fast repetitive supramaximal stimulation were 30.9% and 23.1% in proximal muscles respectively, and 23.0% and 22.5% in distal muscles respectively.

5) In EMG analysis according to severity of symptoms, the more symptoms were severe the more positive finding were noted and toe more decremental ratio was remarkable.

6) The cases in which the duration of symptoms was more than 1 month showed positive EMG findings in 77.9%, but cases with less than 1 month duration showed positive findings in only 12.5%.