In Japan we have had two outbreaks of hand, foot, and mouth disease associated with disorders of the central nervous system, one in 1973 and the other in 1978. The isolated virus in both outbreaks was enterovirus 71. Central nervous system disorders were present in 24% of patients in 1973 and in 8% of patients in 1978. These disorders were localised encephalitis with cerebellar signs as the main feature, aseptic meningitis, and polio-like paresis. The enterovirus 71 isolated in Japan had strong dermatotropic as well as neurotropic tendencies. However in cross-neutralisation tests, no difference in antigenicity from the prototype, BrCr strain, was recognised.