To determine if the ethnocentric perceptions of students would be influenced by participation in a 3-week social studies unit on "The Contributions of Minority Ethnic Groups to American Civilization," a study was made utilizing 114 students in five 12th grade social studies classes (three experimental and two control). The investigation attempted to gain insight into the processes of attitudinal change and to obtain information on the influence of sex, intelligence, and socioeconomic background on attitudinal change. Ten hypotheses were tested. A modified form of the California E Scale was given to all groups prior to the beginning of the study unit, and again three days following the completion of the unit. In addition, the experimental groups completed the Otis Quick-Scoring Mental Ability Tests, Gamma Test: Form C, 1939, and a personal information form. The statistical technique employed was the significance of the differences between means obtained from the same group upon two occasions (t-test). Results of the study were: (1) factual information favorable to minority ethnic groups lowered the expressed ethnocentric attitudes of the experimental groups; (2) both the high and low ethnocentric groups became more tolerant in the expression of their feelings toward members of minority ethnic groups; (3) the male population showed no attitudinal change, but the female population showed highly significant reduction in ethnocentrism; (4) expressed prejudicial attitudes toward minority groups were substantially reduced; and (5) the treatment induced an expressed significant reduction in ethnocentrism in the high socioeconomic group, but there was no significant attitudinal shift in the low socioeconomic group. Recommendations for future research are made. (DB)