THE once promising field of immigration studies has fallen upon hard times. Several able scholars who entered it with enthusiasm ten or twenty years ago have recently abandoned it. Yet the obvious importance of immigrants and their children in the urbanization of America in the twentieth century makes an understanding of their history more vital than ever before. The popularity of general works such as Will Herberg's Protestant, Catholic, Jew (Garden City, N. Y., I960), Samuel Lubell's Future of American Politics (New York, I956), and Nathan Glazer's and Daniel Moynihan's Beyond the Melting Pot (Cambridge, Mass., i963) attests the importance that social workers, religious leaders, urban planners, and politicians attach to the theme. How then are we to explain the flight from a field of scholarship whose pioneer practitioners won an audience as significant as the makers and the readers of such books? One reason, certainly, is the blight of ethnic parochialism, which has done far more damage to studies of twentieth-century immigrants than of earlier ones. The great migrating groups of the nineteenth century-the Irish, Germans, Swedes, and Jews-arrived early enough and in sufficient numbers to play significant roles in the economic and social development of major urban or agricultural regions. The history of any one group, therefore, seemed worth a lifetime of study by several competent scholars, willing to search out both the European background and the American experience of the group. But a solid book about Rumanians, Lithuanians, or Croatians seems hardly as promising a way for a young historian to launch his career today. Indeed, most of the immigrant peoples of the twentieth century gain significance in American history chiefly from the fact of their settlement alongside other nationalities with whom they shared closely parallel experiences in housing, employment, and social adjustment.