Ten years' experience with surgical treatment of thymoma in 52 patients is reported, 25 patients with myasthenia gravis and 27 without. Twenty-five patients had noninvasive tumors (Stage I) and 27 had invasive tumors (Stages II and III). Of the 52 patients, 29 had surgical resection as the only treatment and the remaining 23 had surgical resection with adjunctive preoperative or postoperative radiotherapy. Currently, 39 patients are alive (20 with myasthenia and 19 without), 10 are dead (none dying of myasthenia or tumor), and three patients have been lost to follow-up. The mean follow-up time for all patients was 5.6 years. There were no operative deaths in this series. The 5 year cumulative survival rate for the entire group of 52 patients is 81%; for patients with myasthenia it is 92%; and for those without myasthenia, 71%. This series suggests that the prognosis following resection of thymoma relates primarily to the stage of the tumor and is not significantly influenced by the presence or absence of coexisting myasthenia gravis. The improved survival rate, in contrast to a 1973 report, is a reflection of improved long-term medical management of myasthenia gravis and better postoperative supportive care.