Women are more likely than men to have chest pain suggestive of angina but normal-appearing coronary arteries on angiography, which ultimately imparts a significant morbidity/mortality and economic burden. Recent evidence suggests that women commonly have endothelial and microcirculatory dysfunction, as well as diffusely distributed atherosclerosis--disorders that can cause chest pain, but will not be seen on angiography. This presents an intriguing basis for pathophysiologic differences between women and men, but there are no studies that actually compare the presence of such findings in women with that of men. The objective of this research project is to determine if the incidence of such pathophysiologic differences is truly higher in women than it is in men.