We classified clinically definite multiple sclerosis (MS) patients who underwent brain MRI with superconductive magnet into 2 subgroups: group A, consisting of 14 patients who had shown acute transverse myelopathy (ATM) during the course of illness; and group B, 35 patients without ATM, and the same neuroradiologist, blinded to clinical profiles of the patients, investigated the MR scans. We analyzed some parameters such as distribution, size, shape and number of the lesions. Although the total number of lesions were similar in each group, and the number of small size or patchy shape solitary lesions were not different, the moderate, large, ovoid or confluent lesions were lower in number in group A, compared with group B. The degree of cerebral white matter lesions and periventricular lesions were higher in group B. Brainstem lesions were significantly less common in group A. These results show characteristic differences in MR-detected, possibly pathological, changes between these 2 groups, and support our previous report that group A may constitute a distinct subgroup in patients with MS.