A random population sample of 294 men and 312 women aged 20-64 years, all apparently healthy, were examined following a screening to determine the prevalence of silent ischaemia and its relations to coronary risk factors. Based on exercise testing, the prevalence of silent ischaemia was 2.5% in men and 3.4% in women. In men, silent ischaemia was positively related to systolic blood pressure (P less than 0.001). The other risk factors did not show any significant associations with silent ischaemia. However, the men with silent ischaemia had a higher coronary heart disease risk score, and a tendency towards more symptoms and signs suggesting a poorer health status than the other men and the women. In the 21 men classified as 'hypertensives', silent ischaemia was more common than in the normotensive men (14% versus 2%, P less than 0.001). No such difference was observed in women. In conclusion, silent ischaemia may be a sign of hypertension and a generally increased risk of coronary heart disease in men, but probably not in the majority of women. This further supports that exercise electrocardiography has no role in screening asymptomatic persons for coronary heart disease, probably with the exception of middle-aged men with an increased risk.