An analysis of decommissioning cost studies compared the cost analysis presented in the 1976 National Environmental Studies Project decommissioning study with 18 other government and industry studies of the cost of decommissioning conventional light water reactor generating stations. Six major factors that contributed to the cost differences were differences in the scope of work, the level of detail of the estimate, variations in significant cost factors, inclusion/exclusion of major cost items, plant size and configuration/design differences, and site-specific factors.