The potential causes, immunopathology, and treatment of multiple sclerosis (MS) are summarized in this article. Findings from a well-examined animal model for MS, experimental allergic encephalomyelitis (EAE), are described and used to illustrate the paths of research in MS. Data from a recent clinical trial with a modified myelin peptide provide support for concepts deduced from EAE. The authors stress that the complexity of the disease requires new techniques to capture the influence of single or combined treatment approaches.