One in a series of booklets on world issues, this document evaluates United States policy toward the nations of Nicaragua, Afghanistan, Vietnam, South Africa, Libya, and Iran. Chapter one reviews United States relations with six radical regimes during the administrations of presidents Carter and Reagan and offers a number of lessons about the efficacy of seeking to change the regimes themselves. Chapters two and three discuss various approaches ventured during the years of the Carter and Reagan administrations. Chapter four offers implications for future policy through 10 instructive patterns in the experiences of both administrations. Chapter five suggests conclusions, and among those offered is that whether a nation's goals are primarily global or regional in character, neither regionalist nor globalist doctrine can by itself provide consistently effective policies. The "Talking It Over" section lists discussion questions for students and discussion groups. An annotated reading list concludes the document. (RSL)