Using an ethological observation method (the PC-MC comparison method), this study investigated patterns of reconciliation after aggression among Japanese preschool children, focusing on factors that influenced its occurrence or acceptance, as well as on strategies and function. There were several factors among four-year-olds that facilitated reconciliatory attempts and acceptance, such as proximity after the aggression; among three-year-olds there were no such factors. Depending on the situation during and after aggression, children used ‘explicit’ (e.g., apologizing, compromising, and offering objects) and ‘implicit’ (e.g., being friendly, talking without apologizing, and touching the opponent gently) reconciliatory strategies. Reconciliation occurred more often among friends than among non-friends, particularly among four-year-olds. However, after considering the baseline affiliation level, the conciliatory tendency among non-friends was higher than that among friends in four-year-olds. Victims' self-directed behavior (SDB) - a behavioral index of stress - was elevated following aggression, but decreased following reconciliation. This suggests that reconciliation functions to reduce the post-conflict stress suffered by the targets of aggression. Aggress. Behav. 31:000–000, 2005. © 2005 Wiley-Liss, Inc.