The prognosis of 142 patients with myasthenia gravis (MG) was clinically investigated. Forty-nine (35%) had clinical remission (CR) and 23 (16%) good improvement (GI), while 70 (49%) remained in poor condition. Favorable clinical factors for CR were the onset of MG before the age of 20 years, a pre-thymectomy period of less than one year, and a post-thymectomy period of six years or more. Single-fiber electromyography (SFEMG) showed abnormal jitter in nine (47%) of the 19 CR patients, while abnormal jitter was shown in 13 (81%) of the 16 GI patients. Abnormal jitter in CR patients was correlated with the following clinical factors: complication with the thymoma, a period of three or more years from thymectomy to remission, and a remission period of less than six years. An anti-acetylcholine receptor (anti-AChR) antibody was positive in 12 CR patients (63%) as well as in 13 GI patients (81%). Based upon these facts, we point out that true remission seldom occurs in MG patients, and that there exist clinical features that may favorably induce clinical remission. We would like to postulate that electrophysiological and immunological follow-up is indispensable even in CR patients to predict recurrence.