Patients with myasthenia gravis (MG) have a higher incidence of epilepsy or seizure disorders than general population. Coexistence of MG and epilepsy seems not simply due to chance association. MG was not infrequently considered as a complication of long-term anticonvulsant therapy. In National Taiwan University Hospital, we found 4 out of 251 MG patients who suffered from epilepsy. MG manifestations of these patients did not differ from those in MG patients without epilepsy. There were increased levels of antibody to acetylcholine receptors and association with thymus hyperplasia or thyroid disease. In the literature, we found 25 reported cases with MG and epilepsy. No specific type of epilepsy was linked to coexistence of MG and epilepsy. Possible causes for MG in association with epilepsy are multiple, including drug-induced depression at the neuromuscular junction, anticonvulsant-related immunological changes, and unknown common mechanism to both diseases.