A 63-year-old man died of a brain tumor 29 years after onset of multiple sclerosis (MS). The MS diagnosis was based upon clinical evidence of two brain stem lesions, separate in time, retinal periphlebitis, a fluctuating course of the disease, and supported by the observation of definite cognitive impairment at the age of 41 years, and an increased number of lymphocytes in the cerebrospinal fluid which normalized during gradual recovery. The MS diagnosis was confirmed at autopsy, which also revealed a glioblastoma developing adjacent to typical MS plaques.