The process of immigrant assimilation is typically and uncritically conceived as one of linear progress – becoming similar to the dominant group in the place of destination is presumed to be a good thing. But a compelling body of evidence on the adaptation of immigrants and their children points to a deterioration of outcomes over time and generation in the United States, as well as to nonlinear processes of change. While linguistic assimilation among children of immigrants does proceed rapidly and inexorably as a linear function, other outcomes – in such diverse areas as infant and adolescent health, diet and divorce, delinquency and risk behaviors, educational achievement and aspirations, an ethos of hard work, and the development of an ethnic identity – contradict conventional expectations, expose underlying ethnocentric pretensions, and point instead to assimilation's discontents. By examining such paradoxes of immigrant adaptation that emerge in the conceptual interstices between rhetoric and reality, fruitful reformulations of a seminal sociological concept may be stimulated and advanced.