The author argues that distancing is the dominant response to poor people on the part of those who are not poor and that distancing, separation, exclusion, and devaluing operationally define discrimination. Such responses, together with stereotypes and prejudice, define classism. The article focuses on classism in the United States. Classism is examined in the context of theoretical propositions about the moral exclusion of stigmatized others and is illustrated by cognitive distancing, institutional distancing (in education, housing, health care, legal assistance, politics, and public policy), and interpersonal distancing. The adoption of the Resolution on Poverty and Socioeconomic Status by the American Psychological Association Council of Representatives in August 2000 is cited as an important step in the direction of eliminating the invisibility of low-income persons in psychological research and theory.