The effects of different levels of cooperation on cross-sex and cross-ethnic relationships were compared in two studies. In the first study, 74 sixth-grade students were randomly assigned to three conditions (cooperative controversy, cooperative debate, and individualistic) stratifying for sex, ability level, and ethnic membership. They participated in the study for 55 min a day for 11 instructional days. In the second study, 51 fourth-grade students were randomly assigned to two conditions (intergroup cooperation and intergroup competition) stratifying for sex, ability, and ethnic membership. They participated in the study for 55 min a day for 10 instructional days. An activity report scale was given to students to determine with whom they interacted in structured class activities, unstructured class activities, school activities outside of class, and activities in the home. The results indicate that although there were few differences between the cooperative controversy and cooperative debate conditions in Study 1 (both promoted more positive cross-sex and cross-ethnic relationships than did individualistic learning), intergroup cooperation promoted more positive cross-sex and cross-ethnic relationships than did intergroup competition. The relationships formed within cooperative learning situations did generalize into unstructured class, school, and home activities.