This chapter evaluates scientific racism through the history of race science and the emergence of the eugenics movement. It then moves from a broad look at race science to sociological explorations of race and ethnicity. Specifically, over the generations, sociology has shifted from ignoring race and emphasizing ethnicity, to arguing for the inevitability of assimilation, to the three primary theoretical perspectives in sociology and their approach to the study of race, to the newest theoretical perspectives on race/ethnicity, including racial formations and critical race theory.