Coronary artery ectasia （CAE） is defined as a localized or diffused non-obstructive lesion of the epicardial coronary arteries with a luminal dilation exceeding 1.5 fold of the diameter of the normal adjacent arterial segment. The underlying etiology is variable and includes atherosclerosis, degenerative, congenital, inflammatory, infectious, toxic, and traumatic causes. The severity of the changes in the media correlates positively with the diameter of ectasia. The exact mechanism of its development is unknown, therefore this review is necessitated.