In this paper we review the evidence that angina and 'ischaemic' ST depression can be caused by inappropriate constriction of small coronary artery vessels in patients with microvascular angina (i.e. anginal chest pain with angiographically normal coronary arteries). Although the mechanisms responsible for microvascular dysfunction remain unknown, it is conceivable that the constrictor stimuli may involve vessels which are proximal to those involved in metabolically induced dilation, so that the effect cannot be opposed, at the same site, by the dilator effect caused by ischaemic metabolites. Furthermore, in this review we also present evidence that myocardial ischaemia may result mainly from inappropriate constriction of small coronary vessels, rather than by obstruction of major epicardial coronary arteries. In addition, there are those prone to the condition, such as specific groups of patients with atherosclerotic ischaemic syndromes, including patients with single isolated coronary artery occlusion and no evidence of previous myocardial infarction, patients with single-vessel coronary stenosis who underwent successful balloon angioplasty, and patients with single-vessel disease with detectable abnormal vasomotor responses in non-stenotic coronary arteries.