['We reviewed our experience from 1990 to 2005 to examine whether control of myasthenia gravis (MG) with steroid therapy before surgery could stabilize postoperative respiratory conditions, compared with the nonsteroid treatment.', 'Records of 43 consecutive patients with MG who underwent extended thymectomy at Kansai Medical University Hospital were retrospectively reviewed. Two groups, a steroid group (n = 28) and a nonsteroid group (n = 15) were compared.', 'In the steroid group, steroid doses ranged from 10 to 100 mg every other day, or 40-60 mg daily. The patients showed significantly less thymus hyperplasia in the pathological findings (P = 0.023). Whereas 3 of 28 (7%) in the steroid group suffered respiratory insufficiency within 3 days of surgery, 5 of 15 (33%) in the nonsteroid group exhibited the same problem (P = 0.030). Univariate analysis showed that steroid treatment was the only significant factor (P = 0.041) affecting respiratory insufficiency. Patients in the steroid group achieved palliation of MG more quickly after surgery than patients in the nonsteroid group (86% vs. 57% within 6 months, P = 0.059; 84% vs. 42% within 1 year, P = 0.042).'] Does preoperative steroid therapy stabilize postoperative respiratory conditions in myasthenia gravis?