In an epidemiological multi-centre study, parents filled in the Rutter Parent Questionnaire (RA2) and teachers filled in the Rutter Teacher Questionnaire (RB2) for almost 6000 children. The children filled in the Children's Depression Inventory (CDI). The subjects well represented the entire population of 8-9-year-old children in Finland. The material and design of the study as well as the basic demographic characteristics are presented.