The present study includes externalizing problems, internalizing problems, mother-adolescent relationship quality, and father-adolescent relationship quality in the same structural equation model and tests the longitudinal reciprocal association among all four variables over a 1-year period. A transactional model in which adolescents' internalizing and externalizing problems are negatively related to the quality of adolescents' relationships with their parents and relationship quality is related to internalizing and externalizing problems is hypothesized. Moderation by gender, ethnicity, and parental marital status is also investigated. The sample consists of 246 boys and 253 girls from the sixth and seventh grades of a large public middle school. The study's final model suggests a longitudinal, reciprocal association between the quality of adolescents' relationships with their mothers and internalizing problems. Results suggest longitudinal unidirectional effects from externalizing problems to the quality of adolescents' relationships with their fathers and from the quality of adolescents' relationships with their mothers to externalizing problems. (Contains 4 tables and 2 figures.)