Myasthenia gravis is a disorder of neuromuscular transmission characterized by weakness and fatigue of voluntary muscles. It is now reasonably established to be due to an autoimmune attack directed against the postsynaptic nicotinic acetylcholine receptors of voluntary muscles. Thymectomy has become increasingly important in the treatment of this disease after the successful case of Blalock in 1939. From January 1984 to December 1988, we performed total thymectomy in 25 cases of myasthenia gravis except one, and get the results as follows. l. Among 25 cases, male to female was 10:15 and the age was ranged from 16 years to 65 years. 2. Thymectomy was done in 24 cases and 1 case of malignant thymoma was not resectable. 3. There were 2 deaths after thymectomy due to myasthenic crisis. 4. There were 19 cases [76 %] of improvement after thymectomy as follows; complete remission was 6 cases [24 %], marked improvement was 9 cases [36 %] and subjective improvement was 4 cases [16 %]. 5. The effect of age, and duration of disease on operative result was not statistically significant, but that of thymic pathology was significant.