The aim of the study was to produce data about health behaviour among men born in Northern Finland in 1966. A particular concern was to find out how well health behaviour in adolescence predicts health behaviour in adulthood. The family questionnaire on health and development was submitted in 1980 when the subjects were 14 years of age. The response rate was 97%. The second questionnaire survey was carried out 10 years later with 2500 respondents. The final response rate was 60%. The results indicated that health behaviour in adolescence predicted health behaviour in adulthood as far as smoking and physical exercise were concerned. Over half (65%) of those who were non-smokers in their youth did not smoke as adults. Similarly the majority (71%) of those who had taken physical exercise at least once a week in their youth continued to do so in adulthood. Most of the subjects (85%) used alcohol in adulthood. A good family situation was connected with healthy habits. In the case of drinking, however, the subjects whose fathers belonged to social classes I-II used alcohol to a somewhat greater extent than others. It is important to conceive of health behaviour as an element connected with a person's life situation. Health research should be incorporated into cultural research and should have closer co-operation with other disciplines.