Exposure to air pollution has been shown in epidemiological studies to be closely linked to cardiovascular morbidity and mortality. The exact components of air pollution that underlie the cardiovascular effects are not yet known, but combustion-derived particulate matter is suspected to be the major cause. In controlled exposure studies, we have recently demonstrated that exposure to diesel exhaust causes increased myocardial ischaemia with exercise in patients with asymptomatic coronary artery disease. The mechanism behind this effect is not yet understood, but we have shown that diesel exhaust exposure causes an acute impairment of two important and highly relevant aspects of vascular tone: vasomotor tone and endogenous fibrinolysis. In this study we propose to investigate the effects of exposure to ambient levels of air pollution on patients with stable, symptomatic angina pectoris, during their daily lives.