In autumn 1989, a material of 1,330 men and 1,561 women aged 20-65 years and resident in the County of Vejle replied to a standardized questionnaire about their knowledge and behaviour in relation to prophylaxis of cardiovascular disease. During the same period, 501 men 565 women in the Municipalities of Helsinge and Slangerup participated in a similar investigation. It was investigated whether the behaviours of the participants as regards tobacco, physical activity, diet, experience of stress and overweight were unsuitable in relation to prevention of cardiovascular disease. 22% of the men and 11% of the women had unfavourable behaviour in more than two of these factors. The percentage proportion with many unfavourable factors was greatest among persons with the lowest school education. The majority of the participants were aware of the factors which are of significance for the development of cardiovascular disease. The general level of knowledge was high. A majority of the participants with many unfavourable factors assessed their own risk of development of cardiovascular disease as great. The proportion of the participants who were aware that a personal effort was of significance to retain health was greatest in the group where the behaviour was most suitable both where men an women were concerned.