1. From the Multiple Sclerosis Clinic (Drs. Sadovnick and Paty), University Hospital-UBC Site, and the Department of Medical Genetics (Dr. Sadovnick), University of British Columbia, Vancouver, BC; the Multiple Sclerosis Clinic (Dr. Ebers), University Hospital, University of Western Ontario, London. ON; and the Sunlife Assurance Company of Canada (R.W. Wilson), Toronto, ON, Canada.