Allocated risk of coronary heart disease, from a statistical basis, has traditionally been divided between the effects of a series of well-recognized biological markers (hypertension, elevated serum lipids and cigarette smoking) and the potential contribution of psychological factors, the most prominent of which, in recent times, has been the Type A behaviour pattern. This article examines the possibility that Type A behaviour, as reflected in Jenkins Activity Survey (JAS) Scale scores, influences coronary risk through an effect on these established biological risk markers, either independently or through the mediating influence of occupational dissatisfaction. The data suggest that some scales of the JAS do relate systematically to a composite biological index of coronary risk, and that this relationship can be better understood in terms of lifestyle than stress factors. The implications for the behavioural prevention of coronary heart disease are discussed.