American and Japanese children's evaluations of the reporting of peers' transgressions to authority figures were investigated. Seven-, 9-, and 11-year-old children (N = 160) and adults (N = 62) were presented with vignettes and were asked to evaluate the decisions of child observers who reported their friend's either major or relatively minor transgression to a teacher. The results showed that, in both countries, participants across all age groups considered it appropriate to report major transgressions. However, compared with older participants, the youngest children thought it was appropriate to tattle (i.e., to report more minor transgressions). The results also showed a cross-cultural difference: Japanese compared with American participants considered it appropriate to report minor transgressions. The age-related findings are discussed with reference to children's social experience and improving cognition. The cross-cultural findings are discussed with reference to potential differences in the emphases placed on respecting authority relationships, empathy, and social interdependence by the 2 cultures.