A large Health Survey was carried out in 1984-86 in the county of Nord-Trøndelag. All residents 20 years of age and older were invited to attend, and there was no upper age limit. Totally 74,977 persons have attended (88.1%). In the age group 45-64 more than 95% of the women attended. In cooperation with the district nurses we have studied the non-attendants, based on a 10% sample. The main reasons for not attending were: 1) Many were busy. 2) Some were not interested, 3) Some had moved, 4) Some had health problems. As a group, the non-attendants were less healthy than the attendants, but this was the case for only 12% of non-attendants. These 12%, however, were seriously ill. The data from the Nord-Trøndelag Health Survey are probably the most complete screening data from Norway. The data are especially suitable for epidemiologic studies on blood pressure, diabetes, quality of life, and tuberculosis and other lung diseases. However, the study has also supplied data on cardiovascular diseases, lifestyle, disablement, work and working environment. Several projects in these fields are in progress. The article is based on a report published in 1989.