■ Abstract In this essay, I draw on a professional life history to suggest how sociological knowledge is generated by encounters with changing research opportunities, here called targets of opportunity. In my case, a study of rural communities led to unanticipated conclusions concerning buffering mechanisms that protected authorities by absorbing dissatisfactions and rebellions. Wartime research in a military setting identified sources of group solidarity and effective performance under stress. Major societal changes in racial/ethnic relations provided opportunities to develop new concepts and empirical findings. Synoptic studies of post-World War II American society led to extensive research on values and institutions. These macrosociological analyses of ethnicity and social systems, in turn, led me to a new sociology of war and interstate relations. I also offer here some critical reflections on recurrent issues and chronic controversies in American sociology. Final sections of the review deal with the continuing search for conceptual clarity and cumulative knowledge. I note the obstacles of disciplinary fragmentation, but my closing judgment is that sociology now has the base of substantial scientific knowledge and methodological expertise necessary for investigating crucial twenty-first century problems.By virtue of the editors' generous guidelines, this essay is freed from restraints and can be partly autobiographical-a mode of discourse that all too easily can become both self-serving and misleading. In the present instance, however, some safeguards reside in the fact that the author's involvement in American sociology began in the 1930s and continues now some seven decades later. Thus, biography and history are thoroughly intertwined. Sociology today, of course, differs in many remarkable ways from what it was in the depression years just before World War II. In its organizational embodiment it has moved from a small scholarly organization (the American Sociological Society) to an extensive professional association [the * Historically minded readers should be assured that no close parallelism with the Long Nineteenth Century is intended or implied.