Peel, core and coarsely chop pears. Wash fresh cranberries (removing any debris). In 2 quart saucepan combine all ingredients and heat to boiling. Reduce heat and continue to cook until cranberries pop and sauce starts to thicken. The pectin in the cranberries are what thicken the sauce so be sure they have popped.
Cool at least 1 hour before serving. This can be made up to 2 weeks ahead of service.