The general aim was to study determinants for health behavior. The groups surveyed were: 1) male and female university students, 2) male and female blue-collar workers, and 3) middle-aged men with slightly to moderately elevated coronary heart disease risk factors invited to participate in a 6-month diet and physical exercise program. The research also surveyed the relationships between health behavior, beliefs and knowledge, and the role of demographic, socioeconomic, and personality factors for health behavior and compliance with medical care recommendations. Both among university students and blue-collar workers, women were characterized by having more positive health practices, better health knowledge, and stronger beliefs about the importance of positive health practices than men. A relationship was found between behavior and beliefs concerning the importance of positive health practices, and between knowledge and beliefs, while the link between health knowledge and behavior was weak. Middle-aged men who enrolled, and who declined to enrol, in a 6-month diet and physical exercise program were characterized by different health beliefs and knowledge. Among the participants in the diet and exercise intervention program, reduced compliance with increased intake of dietary fiber was linked to smoking, higher levels of hostility, perception of barriers to dietary change, and poor knowledge of CHD risk factors. Reduced compliance with low fat diet was linked to smoking, younger age, and not having relatives or friends afflicted with CHD. Reduced compliance with the physical exercise program tended to be associated with younger age and having children living at home. Both smokers and non-smokers managed to reduce their estimated CHD risk in the intervention program, but after intervention the smokers still had an elevated coronary risk profile compared to non-smokers. Despite similar knowledge about the health hazards of smoking, smokers gave a lower rating than non-smokers for the importance of not smoking. It was ...