Postoperative respiratory function was evaluated in 94 patients with myasthenia gravis after thymectomy. Preoperative clinical and pulmonary function data were submitted to statistical analyses. The duration of respiratory support and intratracheal intubation time were significantly correlated to % vital capacity, the clinical stage of myasthenia gravis, and the clinical stage of thymoma. Statistical analyses proved that anticholinesterase drugs taken in immediate postoperative period contributed to the improvement of postoperative respiratory function, and non-depolarizing muscle relaxants, i.e. d-tubocurarine which had been considered to be contraindicated in myasthenia gravis was found to be beneficial immediately after the operation in patients with severely deteriorated respiratory function preoperatively.