Myasthenia gravis is present in a significant proportion of patients with thymoma. We investigated particular features of the clinical behavior of thymoma and its relationship to myasthenia in a retrospective study of 79 patients who underwent thymectomy for thymoma during the last 20 years. The presence of myasthenia gravis, Masaoka stage, World Health Organization histotype, myasthenia response, and survival were analyzed. The mean age of the patients was 56.1 ±12.4 years, and 39 had myasthenia gravis. A significantly higher proportion of patients with myasthenia was found in B2 and B3 histotypes compared to A, AB, and B1. Among myasthenic patients, 33.3% had no response, 50% had a partial response, and 16.7% achieved complete remission. During the follow-up period, 16 (21.1%) patients died. Mean survival was 4.8 ± 1.4 years for patients with no myasthenia response, whereas those with a partial or complete myasthenia response had significantly better survival.