This dissertation is divided into three essays. Essay One, "Least-Cost American Diets for the 1980s: The Impacts of Improved Information on Nutrition and Health," addresses the effect of increasing the number of nutritional constraints, for example, amino acids, on an optimal diet. "Health" constraints, which are recommendations to increase longevity and reduce the incidence of certain diseases, are also analyzed. The inclusion of vitamin supplements as an activity is also included. Finally, traditional shadow prie analysis is replaced with cost flexibility analysis;Essay Two, "A Comparison of Type A and Strictly Least-Cost Diets with Plate Waste Considerations and Added Nutrients," addresses the problem of designing least-cost diets for school children in the National School Lunch Program. Strictly least-cost diets are developed with and without consideration to the childrens' revealed preferences towards foods, as indicated by plate waste measures. Constraints to increase the palatability of the optimal diets are included. Optimal diets are differentiated according to age and gender;The third essay, "Least-Cost Diets in U.S. Famine Assistance to Ethiopia," addresses the problem of designing least-cost diets for the severely malnourished in Ethiopia as part of a relief effort from the U.S. through the Agency for International Development. A comparison of optimal diets using the Food and Agricultural Organization's Recommended Daily Allowances (RDAs) and the National Academy of Science's RDAs is made. The effect of using foreign transportation as opposed to domestic transportation is considered. The cost effectiveness of breast feeding is also considered. Finally, a discussion on the provision of least-cost diets during the rehabilitative stage of Protein-Energy Malnutrition is included.