The prevalence of coronary-prone behaviour, Type A, was investigated in a representative sample of all Finnish adults comprising 1941 men and 2168 women aged 30-64 years. The behaviour pattern was assessed by the Jenkins Activity Survey. The mean of the Type A scores was --5.7 for men and --5.8 for women. Among men, 28.3%, and among women 26.8% had scores greater than or equal to 0. Type A was positively associated with the level of education. The prevalence of Type A in Finnish men and women seems to be lower than that found in most other surveys.