Objective: To evaluate magnetic resonance imaging (MRI) of multiple sclerosis (MS) patients in Thailand. Method: A retrospective review on the initial brain and spinal cord MRI in MS patients was done but primary progressive MS and the AQP4 antibody positive patients were excluded. The characteristics of brain and spinal cord MRI were analyzed. Results: For the initial brain MRI studies, fi fty percents satisfi ed McDonald MRI criteria for dissemination in space. For the initial spinal cord MRI, most lesions involved thoracic level and the mean length of spinal cord lesion is 1.29 vertebral body segments (range 0-3). Conclusion: For Brain MRIs in Thai MS patients, there was 50% in sensitivity by the 2005 McDonald’s Criteria for dissemination in space, which is similar to the previous Asian reports. For spinal MRI, the median length of lesions was less than previous Asian reports. This could be due to the fact that AQP4 antibody positive patients, in whom the clinical and imaging features are hard to differentiate from MS patients, were excluded. In other word, the neuromyelitis optica (NMO) spectrum disorders had been more effectively excluded in this study than those in the past. This supports the importance of NMO IgG/AQP4 antibody testing in differentiating MS from NMO spectrum disorders, especially in Asian patients.