We designed this study to evaluate the diameters of the aorta and its major branches in patients who had coronary ectasia. We assigned 80 patients (mean age, 57 +/- 11 yr) with isolated coronary artery ectasia to the study group and 25 patients (mean age, 54 +/- 10 yr) without structural or coronary arterial disease to the control group. All patients underwent coronary angiography and angiography of the aorta and its branches. We used computed quantitative angiography to measure the diameters of the coronary arteries, the aorta, and the major aortic branches. Within the study group, the diameter indices of the proximal portions of the right common iliac artery (P=0.041) and the left common iliac artery (P=0.035) were significantly larger than the diameter indices within the control group. The diameter indices of all other evaluated arteries were similar in both groups (all P >0.05).