The tremendous advances into the genetics and immunology of multiple sclerosis of the past 20 years have led to the development of experimental treatments and therapeutic approaches. With these have come a growing knowledge base and a quickly expanding list of associated terms that has become increasingly difficult for research workers and clinicians to master. Dictionary of Multiple Sclerosis includes over 600 fully referenced terms and definitions from clinical neurology, genetics, molecular biology, biochemistry, immunology, pathology, pathogenesis, epidemiology, radiology, clinical trial methodology, and therapeutics.