The preponderance of genetic factors in attempts to account for susceptibility to multiple sclerosis (MS), a common inflammatory and demyelinating disease of young adults, has recently been demonstrated (Ebers et al. 1995). The inheritance of MS appears to be complex and is believed to involve several genes (Ebers et al. 1996; The Multiple Sclerosis Genetics Group 1996; Sawcer et al. 1996). Methodological approaches to the study of genes conferring susceptibility to MS include association studies, which measure the frequency of a specific allele in affected and healthy populations, and linkage studies, which trace the inheritance of a gene from parents and correlate these genes to disease susceptibility.