In the present study the lesions in MRI imaging were quantified and compared with the clinical and functional abnormalities in 56 patients (27 females and 29 males) with definite multiple sclerosis (MS). The evolution was relapsing in 30, there were relapses followed by progressive evolution in 10, and evolution was progressive from the onset in 16. A good correlation was found between the disability scale EDSS and total lesions in MRI (r = 0.45), and also with the disability scale EDSS and hemispheric (r = 0.45) and centrioval (r = 0.41) involvements and with lesions near the third ventricle (r = 0.32). The clinical parameters predicting a greater surface of involvement in MRI were late onset (beyond 45 years) and progressive evolution. The best correlation between disability scale and MRI lesions was found between EDSS and periventricular (lateral ventricles) lesions (r = 0.46). The linearly correlation between both disability scales was good (r = 0.86), but it improved when an exponential equation was used (r = 0.91). This could allow to use the more simple scale (ISS) with a mathematical transformation. When the patients with a greatest surface of involvement were compared with the remaining MS patients, significant differences were found for nearly all evaluated disability items. Patients with greater involvement surfaces in MRI had greater disability.