The purpose of this study was (1) to evaluate psychometric properties that assess forms of aggression (i.e., relational and physical aggression) across cultures (i.e., Japan and the United States) and (2) to investigate the role of culture in the associations between forms of aggression and social-psychological adjustment problems such as depressive symptoms and delinquency. Participants consisted of 296 fourth-graders (197 Japanese and 99 US children). It was hypothesized that relative to US children, relational aggression would be more strongly associated with depressive symptoms for Japanese children. Findings supported our hypothesis, suggesting that Japanese children may be more vulnerable to negative interpersonal experiences, including relational aggression. (Contains 3 tables and 2 figures.)