We have evaluated chronic corticosteroid treatment in 60 myasthenic patients; 92% were followed for more than 3 years and 82% longer than 4 years. Improvement was noted in 72% of the patients. The best results were seen in those whose symptoms started after the age of 40 years. There was a correlation between the starting dose of prednisone and the rate of improvement. Complete withdrawal of steroids was possible only for 3 patients.