This paper considers the implications for U.S. foreign and strategic policy of the possibility of "nuclear winter," the dramatic cooling of the earth as the result of massive amounts of soot and dust released into the atmosphere by a nuclear exchange. Some ways in which the possibility of nuclear winter affects foreign policy include the following: (1) As a new factor deterring use of U.S. nuclear devices in Europe, it is another reason for NATO nations to doubt the U.S. commitment to their defense. (2) U.S. policy toward Southern Hemisphere nations should take into account that they would become the world's major food suppliers following a nuclear exchange. (3) Given the global nature of nuclear winter, and uncertainty about its intensity or the level of exchange necessary to set it off, U.S. foreign policy may need to become more interventionist to secure, ensure, and enforce peace in nuclear-capable nations. Among the strategic policy implications of nuclear winter are the following: (1) Distinctions such as "tactical" or "theater" among nuclear weapons would cease to exist. (2) Nuclear winter may demand a greater reliance on enhanced radiation and sophisticated conventional weapons. (3) Targeting strategy and deterrent theory would be radically affected. The paper points out the importance of making both superpowers realize the potential seriousness of nuclear winter and incorporate it into their policy thinking.