A 64-year-old man with a 10-year history of Good syndrome had been treated with periodic replacement of γ-globulin. He also had a 6-year history of lichen planus of the tongue. In 2009, the patient was diagnosed as having pure red cell aplasia (PRCA) based on bone marrow aspiration. Thymectomy was not effective. Then, immunosuppressive therapy with PSL and cyclosporine was initiated. Twenty days after treatment painful ulcer appeared on the left side of the tongue. Biopsy specimen of the ulcer demonstrated cells infected with cytomegalovirus and herpes simplex virus. Cytomegalovirus antigenemia was also positive. The tongue ulcer promptly improved after gancyclovir administration for a few weeks. Viral glossitis should be considered as part of the differential diagnoses of oral lesions not only in patients with HIV infection but also in those under immunosuppressive therapy.