This is the fourth annual report in a series 1, 2, 3 that evaluates the adequacy of the fees assessed to cover the federal governments cost for that disposal of high-level radioactive wastes. As with past reports, the fees for commercial spent nuclear fuel are covered. These fees were established under the Nuclear Waste Policy At of 1982. The fees assessed on the commercial nuclear-electric generating industry consist of a one-time fee for waste existing on April 7, 1983 an ongoing fee assessed on subsequent nuclear powered generation. Based on a December 1985 court decision, the contracts covering spent nuclear fuel are interpreted as specifying that the ongoing fee will be assessed on net generation, rather than gross generation. Accordingly, the excess of past ongoing fees based on gross generation over fees based on net generation is assumed to be credited to the utilities during 1986. A presidential decision made on April 30, 1985, directed that a common repository system be used for the permanent disposal of high- level wastes resulting from both atomic energy defense and civilian activities. Thus this report incorporates, for the first time, an assessment of fee adequacy that included the estimated long-term impact of the costs and fees associate with disposal of defense high-level wastes in the Office of Civilian Radioactive Waste Management repository system. In addition, this analysis includes, as a set of alternative cases, an Improved Performance System, a major component of which is Monitored Retrievable Storage facility. Since the cost implications of these features are still being investigate, the conclusions in this report should be regarded as tentative.