This study will examine the safety of Zenapax (daclizumab) in patients with multiple sclerosis (MS). MS is thought to be caused by an over-reactive immune response. T-lymphocytes (cells of the immune system), are thought to damage myelin, a substance that covers the nerve and parts of the spinal cord and is damaged in patients with MS. Interleukin-2 is a natural substance in the body that is necessary for the growth of T-lymphocytes. Zenapax is a genetically engineered antibody that blocks the activity of interleukin-2 and thus interferes with the growth of lymphocytes. Therefore, Zenapax may prevent some of the damage to myelin that occurs in multiple sclerosis.