Objective: To investigate the impact of myasthenia gravis (MG) on the quality of life (QOL) of MG patients. Material and Method: QOL was assessed with SF-36 questionnaire. Results: Thirty-one patients participating in the present study, 74.2% female, with an average age of 44.9 years old. From the SF-36 questionnaire, emotional well being had the lowest score while other components were in average or high range. Ocular and mild generalized MG had better physical functioning than moderate generalized MG. With treatment, those who had no or minimal symptoms had better QOL in both physical and mental aspects. Immunosuppressant was not associated with poor QOL. Conclusion: QOL of Thai MG patients is better than Westerners. However, MG still has significant impact to both physical and mental aspects. More emphasis is needed for mental aspects. The degree of disease control is very important in QOL and the use of immunosuppressant does not impair QOL.