Objective: The Bergen Child Study is a longitudinal study of child mental health from the city of Bergen, Norway. We present methods and results from the first wave of the study, focusing on prevalence of disorders, associations with risk factors, and the use of services. Method: The target population included all 9,430 children attending grades 2 to 4 in Bergen schools during the academic year 2002/2003. The main screening instrument was the Strengths and Difficulties Questionnaire, whereas diagnoses were based on the Development and Well-Being Assessment. Information about child and family risk factors and service use was also obtained in this second stage. Results: In the first phase, the teacher Strengths and Difficulties Questionnaire was obtained for 9,155 (97%) of the target children and the matching parent Strengths and Difficulties Questionnaire for 6,297 (67%); 1,011 children (11%) were assessed with the Development and Well-Being Assessment in the second phase. The weighted prevalence for any DSM-IV psychiatric disorder was 7.0% (95% confidence interval 5.6%-8.5%). Disorders were associated with age, gender, learning difficulties, family type, and poverty. Although 75% of children with attention-deficit/hyperactivity disorder had been in contact with specialist mental health services, this was true for only 13% of those with pure emotional disorders. Conclusions: The overall prevalence of psychiatric disorders in children is relatively low in this Norwegian sample, when assessed with the Development and Well-Being Assessment. Children with emotional disorders have limited access to specialist services. (Contains 5 tables and 2 figures.)