Aim Detection of the relationship of Chlamydia pneumoniae infection and coronary atherosclerosis.Methods Using three primers that recognize conserved sequence on Chlamydia major outer membrane protein genes, Chlamydia pneumoniae was detected in 32 left anterior descending branch of adult atherosclerotic coronary arteries and 7 normal coronary arteries.Results Fourteen of 32 left anterior descending branch of atherosclerotic coronary arteries were PCR positive, positive rate was 43. 75 %; 7 normal coronary arteries were PCR negative, positive rate was 0%.Conclusion There is a significant difference of chlamydia pneumoniae infection between atherosclerotic coronary arteries and normal coronary arteries.