A complementary twofold method of evaluating disability in multiple sclerosis is presented. The first part consists of a graded score on a 0 to 5 or 6 basis assigned to each of 8 functional groups, which are [1] pyramidal, [2] cerebellar, [3] brain stem, [4] sensory, [5] bowel and bladder, [6] visual, [7] mental, and [8] other functions. The second part consists of an over-all Disability Status Scale which is on a 0 to 10 basis. It is this part which permits comparison within or among groups of multiple sclerosis patients over a period of time. This portion is based upon the functional groups in such manner that no status score can be less than the number given in any 1 group; it is, however, independent of the individual groups per se. Applicability of this method of disability evaluation in over 400 patients with multiple sclerosis is described. Theoretic basis for this scheme and the need for this twofold approach are discussed. It is emphasized that the only means of evaluating the severity of multiple sclerosis is a quantitative evaluation of the neurologic deficits caused by this disease.