An asymptomatic anterior mediastinal mass in a 22-year-old man proved to be nodular sclerosing Hodgkin's disease of the thymus gland. Complete excision was possible via a left posterolateral thoracotomy. Postoperative chemotherapy was given. Follow-up after 1 year showed no residual disease. Nodular sclerosing Hodgkin's disease is an uncommon tumor of the thymus gland and should be incorporated in the differential diagnosis of anterior mediastinal tumors. Multimodality treatment is advocated.