The project aims at studying the role of behavior problems and social competence in girls' and boys' exclusion and inclusion throughout child care and in the transition to primary school. A particular focus regards the elucidation of developmental mechani sms. The main hypotheses to be studied are: (a) behavior problems predict exclusion, and social competence predict inclusion in child care and in the transition to primary school; and (b) distinct developmental trajectories of behavior problems and social competence have specific predictions for inclusion and exclusion. The project will utilize an extant rich data set from an ongoing longitudinal study of 1159 children, which includes multi-informant, multi-method measures of behavior problems and social competence, exclusion and inclusion, family and child background, and child care and school factors. In addition, we will collect new data central to the project's objectives children's age 5 and after school entry. Multiple regression, structural equatio n modeling, latent growth curve analyses, and growth mixture modeling will be employed to address the research issues. Findings will inform policy on early prevention, and intervention as well as child care, child welfare and primary education. The projec t is of particular relevance for the research program on Welfare, Work and Migration (VAM). Persistent behavior problems and concomitant learning difficulties are an important source of failure in early education, which puts children at risk for exclusion and marginalization. The project applies in particular to the thematic areas of family and society, children's developmental conditions, and the mechanisms of marginalization. We pay special attention to behavior problems in girls, their concomitants and consequences, incorporating the gender perspective of the program plan.