Since the beginnings of what later became the United States, intergroup relations based on ethnic and racial background have played a powerful role in shaping both interaction and opportunity. A minority group is a subordinate group whose members have significantly less control or power over their own lives than members of the dominant or majority group have over theirs. The term racial group describes a group that is set apart from others because of physical differences that have taken on social significance. Ethnic groups are set apart from others primarily because of their national origin or distinctive cultural patterns. Race as a biological category does not exist. The racial categories we typically take for granted grow out of sociocultural traditions and historical experiences that are specific to various groups. Racial formation is a sociohistorical process in which racial categories are created, inhibited, transformed, and destroyed. In this process, those who have power define groups of people according to a racist social structure. The social construction of race refers to the process by which people come to define a group as a race based in part on physical characteristics, but also on historical, cultural, and economic factors. Stereotypes are often used to justify unequal access to resources. In the 2000 census, over 7 million people reported that they were of two or more races. The distinction between racial and ethnic minorities is not always clear-cut.

Prejudice is a negative attitude toward an entire category of people. Sometimes prejudice results from ethnocentrism—the tendency to assume that one's own culture and way of life represent the norm or are superior to all others. Racismis one important and widespread form of prejudice that fosters a belief that one race is supreme and all others are innately inferior. In 2006, more than half of the 7,400 hate crimes reported involved racial bias. Discrimination is the denial of opportunities and equal rights to individuals and groups because of prejudice or other arbitrary reasons. The glass ceiling refers to an invisible barrier that blocks the promotion of qualified people in a work environment based on their gender, race, or ethnicity. Racial profiling is another form of discrimination. Dominant groups enjoy privileges at the expense of others. Sociologists are becoming increasingly interested in what it means to be "White," because White privilege is the other side of the coin of racial discrimination. Institutional discrimination is the denial of opportunities and equal rights to individuals and groups that results from the normal operations of a society. Affirmative action programs have been instituted to overcome past discrimination.

Prejudice and discrimination help to preserve the existing system of inequality. Exploitation theory argues that such practices are a basic part of the capitalist economic system. According to the contact hypothesis, in cooperative circumstances, interracial contact between people of equal status will cause them to become less prejudiced and to abandon old stereotypes.

There are six characteristic patterns of intergroup relations. Genocide is the deliberate, systematic killing of an entire people or nation. Expulsion is the systematic removal of a group of people from society. Amalgamation describes the end result of intermarriage over several generations when a majority and a minority group combine to form a new group. Assimilation is the process by which a person forsakes his or her own cultural tradition to become part of a different culture, as is practiced by minorities when conforming to the standards of the dominant group. Segregation refers to the physical separation of two groups of people in terms of residence, workplace, and social events. Pluralism is based on mutual respect for one another's cultures among the various groups in a society.

The largest racial minorities in the United States are African Americans, Native Americans, and Asian Americans. As of 2006, 24.3 percent of African Americans were living in poverty compared to 8.2 percent for Whites. Native Americans represent a diverse array of cultures. There are approximately 2.4 million Native Americans in the United States. Asian Americans are often held up as a model or ideal minority group, supposedly because they have succeeded economically, socially, and educationally despite past prejudices and discrimination. By some estimates, there are up to 3 million Arab Americans in the United States. Most are not Muslim. Latinos represent the largest minority in the United States. In 2006, there were more than 44 million Hispanics in this country. Jewish Americans constitute about 2.2 percent of the population of the United States. This is the world's largest concentration of Jews. White ethnics make up a significant segment of the U.S. population.

Worldwide, immigration is at an all-time high. Globally, these mass migrations have had a tremendous social impact. One consequence of global immigration is the emergence of transnationals—people or families who move across borders multiple times in search of better jobs and education. Clear racial and ethnic biases have been built into immigration policies.