poliovirus, echoviruses and enteroviruses 68 to 71. These may be the cause of hand-foot-mouth disease (HFMD) (Coxsackie virus A16, enterovirus 71) (1), herpangina (enterovirus 71), hemorrhagic conjunctivitis (enterovirus 70, Coxsackie virus A24) (2), poliomyelitis (poliovirus), polio-like paralysis or radiculomyelitis (enterovirus 70, enterovirus 71, Coxsackie virus A7 and A24) (3, 4). The HFMD caused by coxsackie virus A16 or coxsackie virus A10 is usually a mild, self-limiting illness that primarily affects infants and young children and there are usually no central nervous system (CNS) complications (5). Yet enterovirus 71 (EV 71) may cause not only HFMD, but also various neurologic complications such as aseptic or viral meningitis, encephalitis or polio-like paralysis (6). Especially, EV 71 meningitis or encephalitis can occasionally be fatal (7). The non-contrast enhanced MR imaging findings of EV 71 encephalomyelitis were first published in 1999 by Shen et al. (8). The MR imaging features such as brainstem involvement and an abnormal signal on a T2weighted image (WI) were described in this article. However, to the best of our knowledge, there have been few reports about the MR features on contrast enhanced T1-WI and the diffusion weighted image (DWI) of EV 71 encephalitis in infants with HFMD. We report here on the MR imaging findings of a case of acute EV 71 encephalitis that involved the brain stem J Korean Soc Radiol 2011;64:113-116