This study, directed by the Food Security Act of 1985, examines the supply of and demand for imported casein in the United States and the effects on the dairy price support program of possible actions to limit imports. A 50-percent quota (based on average 1981-85 imports) would cause casein prices to rise to a price equivalent to nonfat dry milk, replacing much casein with soy, whey, and other proteins. It would raise ingredient costs of cheese analogs to about the level of natural cheese and perhaps, replace some analogs with natural or processed cheese. A 50-percent tariff would raise casein prices and shift many users to soy, whey, or other ingredients, but not reduce CCC costs.