In the past, the relationship between coronary artery disease (CAD) and been studied extensively. The ABO blood group has a significant effect on homeostasis and is therefore associated with adverse cardiovascular events. This study aimed to determine the distribution of ABO blood group and rhesus (Rh) status (ABO/Rh) in patients with different severity of CAD in Iranian community. A total of 1,236 CAD patients undergoing angiography were evaluated and their ABO/Rh blood type was determined in a study center between February 2005 and December 2010. Of the 1,236 records, only 1,046 medical documents recorded the number of involved vessels. The patients were classified according to the number of significantly affected stenotic vessels into single vessel (1VD), two vessels (2VD), and three vessels (3VD) disease subgroups. A substantially different ABO/Rh blood groups distribution was seen in the examined samples (O: 29.7%, A: 39.7%, B: 22.2%, AB: 8.3%, Rh positivity: 89.2%). The ABO/Rh blood group phenotype distribution in CAD patients with 1VD, 2VD, and 3VD was as follows: 37.5%, 41.3%, and 41.5%, respectively, for group A; 24.1%, 20.5%, and 20.6%, respectively, for group B; 31.2%, 26.8%, and 30.2%, respectively, for group O; 7.1%, 11.4% and 7.7%, respectively, for group AB (p = 0.26), and 88.7%, 90.5%, and 87.6%, respectively, for Rh positivity, (p = 0.47). In addition, no significant correlation was not found among the ABO/Rh blood group distribution and the number of vessels involved, however, according to the different distribution of ABO/Rh blood group in CAD patients and healthy population, ABO/Rh might have an unknown role in CAD patients.
 Keywords: Coronary artery disease, Blood group, Stenosis, Vessel, Rhesus.