We report 2 cases of thymomatous myasthenia gravis associated with postoperative crisis and medicated with steroid therapy using prednisolone without primary dose escalation. Two women, a 38 years old and the other 64 years old, underwent extended thymectomy under the diagnosis of myasthenia gravis associated with invasive thymoma. Bulbar symptoms in both were severe despite preoperative anticholinesterase medication. Myasthenic crises with an antiacetylcholine receptor antibody (anti-AchR Ab) elevation were encountered in the postoperative clinical course. Daily administrations of a large amount of prednisolone without primary dose escalation and the subsequent tapering therapy effectively improved myasthenic symptoms and decreased their anti-AchR Ab titer. We also discuss difficulties in treatment in these cases.