Acute transverse myelitis is a monophasic disorder, the recurrence of which raises the question of multiple sclerosis (MS) or other multifocal CNS disease. We now report three patients with a previously undescribed syndrome of relapsing isolated acute transverse myelitis. Each had two to five attacks over periods of 3 to 8 years, characterized by ascending paresthesias, urinary retention, sensory loss with a thoracic or cervical level, paraparesis, hyperreflexia, and bilateral Babinski signs. MRI demonstrated areas of increased signal intensity on T2- and proton density-weighted scans and decreased signal intensity on T1-weighed scans of the cervical or thoracic spinal cord consistent with an inflammatory or demyelinating process. All patients had normal complete myelograms, oligoclonal IgG bands were consistently absent from the cerebrospinal fluid, cranial MRIs were normal, and there was no other clinical or laboratory evidence of MS, collagen-vascular disease, or active viral infection. They were treated with high doses of intravenous corticosteroids, stabilized between episodes, and had partial or complete recovery. The recognition of these three patients at a single medical center in a 1-year period suggests that relapses of acute transverse myelitis may not be rare.