A 26-year-old male with chronic myelocytic leukemia was admitted for unrelated allogeneic bone marrow transplantation (BMT). After BMT, he developed swelling of biateral submandibular glands accompanied with pneumonitis possibly due to cytomegalovirus (CMV). Biopsy from the left submandibular gland showed giant cells with nuclear inclusion bodies that were positive for anti-CMV-IE monoclonal antibody, there fore cytomegalic sialoadenitis was diagnosed. The administration of ganciclovir resulted in resolution of the pnumonitis and submandibular gland swelling. Although cytomegalic sialoadenitis is not a life-threating complication in BMT patients, it should be noted that biopsy is very useful for the diagnosis of systemic cytomegalovirus infection.