The study found that low socioeconomic position was associated with more mental health problems and more life stressors. Both environmentally related and person-related stressors predicted mental health problems independently of socioeconomic position. The associations between socioeconomic position and all mental health outcomes were partly mediated by environmentally related life stressors. The extent of mediation was larger for emotional problems than for behavioral problems. Because the effect sizes of the associations were relatively small, targeted interventions designed to prevent impaired mental health may have only modest benefits for adolescents with low socioeconomic backgrounds. Subjects were participants in the TRacking Adolescents' Individual Lives Survey (TRAILS), a prospective cohort study of Dutch preadolescents aimed at explaining the development of mental health problems from preadolescence into adulthood. Sample selection involved five municipalities in the north of the Netherlands, including both urban and rural areas. Trained interviewers visited parents/guardians at their homes to conduct interviews that addressed a wide range of topics, including their socioeconomic position and their children's mental health. At both time one and time two, the children completed questionnaires at school under the supervision of TRAILS staff. The teachers also completed a brief questionnaire for all TRAILS children in their classes. Eighteen person-related life stressors were measured, including chronic illness/handicap, fewer friends than desired, bullying, severe family conflict, and problems at school. Nineteen environmentally related life stressors were measured, including housing problems, neighborhood problems, parental unemployment, and death of a family member. 2 tables, 2 figures, and 32 references