We report five cases of cytomegalovirus infection in immunocompromised patients which were detected by either cytomegalovirus antigenemia assay or in situ hybridization. Four cases had leukemia and the other had chronic renal failure. All the three BMT recipients suffered from GvHD. Interestingly, there was an unique case of CMV disease without a history of BMT, which reminded us that CMV could attack immunocompromised patients who had not undergone transplantation, too. Four out of five cases died. We think that cytomegalovirus infection or disease should not be regarded as a minor problem in post-transplantation infection in Korea.