Third- and sixth-graders discussed moral dilemmas involving altruism and honesty in groups composed of four same-sex classmates. For each dilemma, the children tried to agree on what the main character should do. Before and after the discussions, each child responded to the dilemmas independently. In a control condition, children responded to the dilemmas before and after discussions of nonmoral topics. The discussions were videotaped, and no adults were present. Following the discussions of the moral dilemmas, children shifted toward a stronger preference for the altruistic alternatives in the altruism dilemmas and a stronger preference for the dishonest alternatives in the honesty dilemmas. The shifts in preferences were related to the frequency with which children in each group had stated opinions favoring each alternative and given reasons for each alternative during their discussions. The relations suggest that children considered both their peers' judgments about the most acceptable choice and the arguments for these judgments. The response shifts were also related to the frequency of affective behaviors (e.g., verbal aggression, commands, and laughing or joking). In boys' groups, choices of the altruistic alternatives were less likely when the group discussions were less orderly and controlled.