Since the inception of the MS Clinic, Vancouver Hospital and Health Sciences Centre, all consecutive, unrelated patients with multiple sclerosis (MS) have had their family histories documented by the Clinic's geneticist as part of the overall assessment. The family histories are updated annually. These data, along with the longitudinal clinical information on each patient, have resulted in a unique resource for clinical genetic/genetic epidemiological/molecular genetic researh on MS. Analyses of these data have included the calculation of age-adjusted familial risks for MS; genetic modeling, necessary for molecular genetic research; and family studies involving affected relative pairs, studies of the nontransmitted parental haplotypes, and multiplex families. The results of the work to date are discussed. In addition, the impact of these data on the development of the Canadian Collaborative Project on Genetic Susceptibility to Multiple Sclerosis is reviewed. This project involves all 14 MS “sites” across Canada, and the study's overall objective is to elucidate the roles of genetic and environmental factors in the causation of MS.