We report a 39-year-old female patient known to have multiple sclerosis (MS), who later developed cerebral glioblastoma. The tumor was documented on the brain-magnetic resonance imaging (MRI) during the work-up for an apparent relapsing MS, and was subsequently confirmed pathologically by stereotactic biopsy and the postmortem brain examination. Our case, as well as others, re-emphasizes the need to evaluate the symptoms and brain MRI carefully, even in well-documented MS subjects. The concurrence of MS and intracranial glioma is uncommon. The possible relationship between the 2 diseases was discussed, and related literature reviewed.