We examined 148 EEG recordings from 118 patients affected with myasthenia gravis (35 males and 83 females, aged 17-82, with illness durations between 1 month and 24 years). The cases were clinically evaluated according to Ossermann's classification at the time of EEG recording. EEG patterns were subdivided into normal, diffuse or focal slow abnormalities, or epileptiform patterns. Of the 118 patients, 104 had normal EEG recordings and 14 had at least one abnormal recording (8 diffuse slow abnormalities, 6 focal slow abnormalities). The EEG findings were not correlated with clinical parameters (thymic pathology, respiratory incidents, drug treatment, etc.). One patient (whose EEG recordings were normal) showed an isolated epileptic fit and another patient was affected by epilepsy. A possible relationship between the two diseases is discussed.