By virtue of an understanding of hemostasis and coagulopathy using modern techniques, the exact role of individual serum protein in vascular thrombosis or hemorrhage becomes more apparent. Cryoglobulin causes vasculitude and thrombosis in various vascular beds, but its role in brain hemorrhage is unknown. We encountered a cryoglobulinemic patient to have cryoglobulinemia, hypocomplementia, and cerebellar hemorrhage during a reactivation of cytomegalovirus infection. Because cryoglobulin is harmful to vessel and hemostasis, and often increases nonspecifically in response to incitement, its weight in vascular syndrome must seriously be reviewed. Coagulopathy in a reactivation of latent virus such as cytomegalovirus should be cautioned in older patients.