The United States General Accounting Office (GAO) studied the processes used by the National Academy of Sciences to produce two reports on the relationship of diet to health: "Toward Healthful Diets" (1980), and "Diet, Nutrition and Cancer" (1982). Because the reports differed about whether the public could reduce its chronic disease risk through dietary changes, the GAO obtained information on the Academy's processes of providing reports in controversial areas. This report presents information on the range of scientific fact and judgment on the relationships of diet to cancer and heart disease, outlines the controversies, explains the issues, and giving background on the various points of view involved. The scientific methodology or validity of the reports' recommendations were not evaluated for this report. The report's two major sections discuss how and why the two reports were developed, and how and why the reports are both similar and different. The appendixes include comparisons of dietary recommendations made in the reports, as well as comments from health authorities. (JD)