No treatment has been found which reverses long-standing neurological dysfunction in patients with multiple sclerosis (MS). Observations in animal models of MS show that immunoglobulins directed against CNS components promote oligodendroglial proliferation and new myelin synthesis. Preliminary studies in inflammatory-demyelinating diseases of the human peripheral and central nervous system suggest that the repeated intravenous administration of polyclonal human immunoglobulin (IVIg) is sometimes followed by clinical improvement. A randomised, placebo-controlled, double-blind, clinical trial was designed to test the hypothesis that repeated administration of IVIg will result in a meaningful degree of recovery of apparently irreversibly lost neurological function (weakness). A total of 76 patients with MS will participate in the study. These patients had developed a fixed, apparently permanent weakness that had not improved in the preceding four to 18 months. If effective, IVIg administration may benefit the large proportion of patients with MS who have active disease by enhancing the potential for myelin repair in the evolution of the inflammatory-demyelinating lesion.