OBJECTIVES: To compare the effect of low-dose prednisolone (PSL) (≤5 mg/day) and high-dose PSL (>5 mg/day) therapy on the QOL and activity of daily living (ADL) in patients with MG. METHODS: A total of 679 patients with MG underwent a survey using Japanese versions of the MG-QOL 15-J and MG-ADL scales. Higher scores of these scales suggest deterioration of the QOL and ADL, respectively. RESULTS: The total MG-QOL 15-J scores of the high-dose group (27.0±13.8) were significantly higher than those of the low-dose group (20.9±14.6). Similarly, the total MG-ADL scores of the high-dose group (6.3±4.1) were significantly higher than those of the low-dose group (5.3±4.1). CONCLUSION: These results showed that the QOL of patients in the low-dose group appeared better than that in the high-dose group. Low-dose PSL therapy may help achieve minimal manifestations level in Japanese patients with MG.