We present the design of a double-blind, randomised placebo-controlled phase III study to evaluate safety and efficacy of IVIG in the treatment of patients suffering from primary or secondary chronic progressive multiple sclerosis. The primary endpoint is disability. Two measures of disability were chosen in order to assess the primary end point (a) sustained improvement (assessed at month 6, confirmed at month 9) and (b) progression to increasing disability of the disease (sustained for 3 months) at any time during the course of this 2 years study. The disability is measured by the Extended Disability Status Scale (EDSS). Secondary end points include the assessment of visual function, functions of the upper extremity, cognitive functions, depression and quality of life.