A review of the evaluation, treatment, and end results for 52 patients with thymoma treated at The University of Texas M.D. Anderson Cancer Center (1950-1984) is presented. The objective of the study was to examine the influence of a number of clinical characteristics on survival, including histologic and staging classifications, associated diseases, symptom status, and treatment. Forty-nine patients (94%) underwent surgical exploration; 13 were stage I, 12 were stage II, and 24 were stage III. Complete resection was accomplished in all of the stage I and II groups and in 6 of the stage III patients. An asymptomatic history, surgical stage I disease, lymphocytic thymoma cell type, and complete resection favorably influenced prognosis. The cumulative 5-year survival rate for all patients was 40%. No patient with stage I thymoma had recurrent disease, however, there were 9 recurrences (50%) in the completely resected stage II/III patients, six of whom remained disease-free following treatment with radiotherapy, chemotherapy, or a combined approach.