The clinical characteristics and course of acute transverse myelopathy (ATM) was studied. One patient developed multiple sclerosis. In 1 patient ATM was caused by tumour-cell embolization of the intramedullar vessels; 30 aged 12-74 years (median 36 years) had ATM of unknown course, of these, 13 had symptoms of a preceding viral-like infection, 18 had back-pain and 10 signs of spinal shock. The time from onset of ATM to maximum deficit varied from less than 1 h to 20 days. The thoracic region was the most common level of cord damage. Follow-up was possible in 29 cases; 2 died (2 and 8 months after onset), of the surviving 27 (follow-up 1-13 years, median 6 years) one third had a good outcome, one third a fair, while one third remained paraplegic, incontinent with severe sensory deficits. Back-pain and signs of spinal shock indicated a poor outcome.