Asian immigrants to the UK have a higher mortality from coronary artery disease (CAD) than native Caucasians. There is a clinical impression that Asians have smaller coronary arteries than Caucasians. In the present study, consecutive series of 72 male Caucasian and 70 male Asian patients undergoing diagnostic coronary angiography were recruited. Measurements of proximal disease-free segments of the three major coronary arteries were made using the catheter tip as the calibrating object. Electronic callipers were used for all measurements. Total coronary artery diameter was derived by adding the diameters of right, left anterior descending and circumflex arteries. Asians had significantly smaller total vessel diameter compared to Caucasians. They also had smaller body surface areas. This observation has important therapeutic implications regarding coronary intervention in this ethnic group already suffering excess mortality from CAD.