The large-scale international migrations of the past decade are of increasing relevance to the formulation of foreign policy. The nature of such migrations has undergone dramatic transformations from those of the quite recent past, and the last five years have seen a series of migration “crises” with powerful foreign-policy implications. Foreign policies have had dramatic effects upon international migration trends. Usually these effects have been unintended and unanticipated, though mass migration has sometimes been employed as a tool of foreign policy. At the same time, international migration has had significant impact upon the formulation and content of foreign policy, especially in the United States. These relationships now present complex policy choices, involving deeply entwined concerns of foreign, domestic, and humanitarian complexion. There are important lessons to be learned from recent experiences, lessons that challenge longstanding perspectives. Indeed, real peril now attends the failure to deal coherently and humanely with international migrations as they relate to foreign policy.