The neuropathology has been described of chronic, relapsing experimental allergic encephalomyelitis produced in SJL/J mice given two injections of isogeneic spinal cord in complete Freund's adjuvant, 1 week apart. The inducing inoculum contained no Bordetella pertussis. The central nervous system changes included hemorrhagic lesions and significant nerve fiber depletion during the early stages of disease, demyelination followed by remyelination, influxes of polymorphonuclear leukocytes and hemorrhage with each acute episode, extensive gliosis, and some Schwann cell invasion and myelination within the central nervous system. Since the mouse is a highly accessible species that is immunologically well understood, this model might lend itself to fuller dissection of autoimmune events associated with recurrent demyelination, problems of considerable significance to multiple sclerosis research.