Aim To study the effects of chronic infection of microorganism on bypass vessels. Methods To detect C pneumoniae (CP), H.Pylori (HP), and cytomegalovirus (CMV) in great saphenous vein, internal mammary artery and radial artery by polymerase chain reaction (PCR). Results Venosclerosis rate in great saphenous vein is 69.6%, arteriosclerosis rate in internal mammary artery and radial artery are 65.0% and 73.3%, respectively. They are not different in statistics(χ 2=0.397,P=0.82); positive rates of CP, HP, CMV in great saphenous vein are 13.0%, 8.7% and 0.0%, in internal mammary artery are 25.0%, 35.0% and 0.0%, and in radial artery are 26.7%, 23.3% and 16.7%; positive rates of CP, HP, CMV in radialartery are higher than in great saphenous vein (p<0.05, respectively), HP in internal mammary artery is higher than in great saphenous vein (p<0.05). Conclusions Degrees of arteriosclerosis are not different among great saphenous vein, internal mammary artery and radial, we had beter to choose great saphenous vein in CABG, and then internal mammary artery or radial artery from infection of microorganism.