This study tested culture-general and culture-specific aspects of adolescent developmental processes by focusing on opportunities and peer support for aggressive and delinquent behavior, which could help account for cultural similarities and differences in problem behavior during adolescence. Adolescents from 12 cultural groups in 9 countries (China, Colombia, Italy, Jordan, Kenya, the Philippines, Sweden, Thailand, and the United States) provided data at ages 12, 14, and 15. Variance in opportunities and peer support for aggression and delinquency, as well as aggressive and delinquent behavior, was greater within than between cultures. Across cultural groups, opportunities and peer support for aggression and delinquency increased from early to mid-adolescence. Consistently across diverse cultural groups, opportunities and peer support for aggression and delinquency predicted subsequent aggressive and delinquent behavior, even after controlling for prior aggressive and delinquent behavior. The findings illustrate ways that international collaborative research can contribute to developmental science by embedding the study of development within cultural contexts.