Women with cardiac chest pain indicated by signs and symptoms of myocardial ischemia in the absence of obstructive CAD are often labelled as cardiac syndrome X (CSX). A subset of patients with CSX may have symptoms of ischemia due to microvascular dysfunction. Angina due to microvascular coronary dysfunction (MCD) is an etiologic mechanism in women with vascular dysfunction. New data provide improve understanding of coronary vascular dysfunction and resultant myocardial ischemia that characterize MCD among patients with cardiac syndrome X. MCD has an adverse prognosis and health care cost expenditure comparable to obstructive CAD. The high prevalence of this condition, particularly in women, adverse prognosis and substantial health care costs, coupled with a lack of evidence regarding treatment strategies, places MCD as a research priority area.