After a careful differential diagnosis of 264 consecutive cases of spinal cord syndrome seen over a period of 10 years, no diagnosis was reached in 72 patients. Of these cases, known as myelopathy of unknown etiology (MUE), 57 were followed-up for a mean of 2.33 years, 50 being chronic cases and 7 acute cases. Diagnosis was reached in 29 (58%) of the 50 chronic cases, the remaining 21 (42%) still being of unknown etiology. The most frequent diagnosis was either definite or probable multiple sclerosis (MS). Magnetic resonance imaging (MRI) was of great value in detecting asymptomatic brain lesions. We conclude that after a long clinical follow-up and the use of MRI we were able to diagnose more than half the previously MUE patients.