The effectiveness of a conflict resolution training program was examined in an American midwestern suburban elementary school. Participants were 80 kindergartners randomly assigned to an experimental or control condition in morning or afternoon time blocks. Children in the experimental condition received 9 hr of conflict resolution training integrated into a curriculum unit on friendship taught daily for 4 consecutive weeks. Children in the control condition were taught the identical friendship unit for the same period of time without conflict resolution training. Teachers rotated equally across conditions. Significant differences between trained and untrained children occurred in their knowledge and retention of the conflict resolution procedure, willingness and ability to use the procedure in conflict situations, and conceptual understanding of friendship.