Multiple sclerosis (MS) is an autoimmune disorder characterized by CNS inflammation, demyelination and cellular damage with atrophy. Most patients with MS initially present with a relapsing-remitting course, with periodic episodes of neurologic symptomatology that do not follow a predictable pattern. In order to maintain a stable clinical course, it is felt to be important to control the number and severity of relapses, as disability, at least in part, is a cumulative effect of damage from multiple lesions within the brain and spinal cord. Historically, MS has not been considered curable, because the immune system could not be adequately normalized over the course of a lifetime. Alemtuzumab (Campath-1H; Campath(®), Genzyme, MA, USA) has recently been investigated in a Phase II clinical trial in the treatment of relapsing-remitting MS. The results observed in the study are very encouraging and multiple insights have been made into the nature of autoimmunity in general based on the clinical response to this monoclonal antibody. Enrollment in two pivotal Phase III clinical trials of alemtuzumab in MS is now complete.