Background There are three monocyte subsets in human. Classical monocyte(CD14+CD16-) has been known as inflammatory monocyte, however, the role of non classical monocyte(CD14loCD16+) is not clear yet. We tried to investigate the relationship between coronary artery disease severity and the pattern of monocyte distribution. Methods We analyzed 93 whole blood samples using flow cytometry(M:F=59:40, mean age: 64 yrs). The subjects taking statin were excluded because statin can reduce CCR2 expression. Results The monocyte distributions were not different with aging. There were no significant differences in monocyte subsets between DM and non DM patients. As a whole, the proportion of classical monocyte was lower in 3 vessel disease compared to 1 or 2 vessel disease(p<0.05) but this difference was not proved by post hoc analysis. Instead, the ratio of classical monocyte/non classical monocyte was significantly higher in 3 vessel disease compared to normal coronary artery(6.89 vs 2.86, p<0.05). Conclusion The ratio of classical monocyte/ non classical monocyte rather than absolute proportion of classical monocyte or non classical monocyte might be more closely associated with coronary artery disease.