Catastrophic longitudinal myelitis is an extremely rare neurologic manifestation of collagen vascular disease, described heretofore in 11 cases of SLE and 1 of Sjogren's Syndrome. This report documents markedly abnormal and worsening CSF findings on sequential CSF examinations over a period of three days (WBC >1500 cells/microL, >80% neutrophils, markedly elevated protein, and extremely low glucose levels) in the absence of infection. These abnormalities cleared rapidly with institution of immunosuppressive therapy so that a third CSF exam done within three days revealed almost complete normalization of CSF values. These findings suggest that in some cases of CLM a strong inflammatory component may be present, while in others, other pathogenic factors may predominate.