When children apologize, they accept responsibility for wrongdoings and act to reconcile social relationships. Apologies to siblings were coded in 40 families that were observed for 9 h when children were 2 1/2 and 4 1/2 years old, and again 2 years later. We found that sibling apologies were rare, generally simple in form, and more frequent after physical harm than after rights violations or verbal harms. Spontaneous apologies were more frequent than apologies mandated by parents, and spontaneous apologies increased with age, as did reconciliation following apologies. By 6 years of age, children reacted more favorably to spontaneous than to parent-mandated apologies, demonstrating their sensitivity to this one index of the apologizer's sincerity.