Inoculation of mice with most neurotropic strains of the coronavirus mouse hepatitis virus results in an immune response-mediated demyelinating disease that serves as an excellent animal model for the human disease multiple sclerosis. Recent work has shown that either virus-specific CD4(+) or CD8(+) T cells are able to mediate demyelination and also that the antibody response is crucial for clearing infectious virus. Another exciting advance is the development of recombinant coronaviruses, which, for the first time, will allow genetic manipulation of the entire viral genome.