In considering health information systems, great hope is attached to the use of child health records as a data source for research and community planning. In order to test the completeness of child health records data and their agreement with other sources, information about living conditions, use of medical services and health problems in preschool children were studied in 707 child health centres' records. The results show a considerable number of deficiencies in the system which could, to a certain extent, be remedied by improved instructions to the staff. Health problems in the area of child care also need to be fully defined.