Fourteen epithelial thymomas and eight granulomatous thymomas were studied in order to clarify the clinicopathological relationship of these diseases. The age distribution, histological picture and clinical course of granulomatous thymoma were quite different from those of epithelial thymoma but similar to those of the nodular sclerosing type of Hodgkin's disease. Granulomatous thymoma should therefore be distinguished from epithelial thymoma and perhaps called Hodgkin's disease of the thymus.