Abstract: AIM:To observe the expression of CD44 on the surface of peripheral blood mononuclear cells (PBMC) in patients with different types of coronary heart disease (CHD) and to investigate its clinical significance. METHODS: Thirty normal subjects, 26 patients with stable angina pectoris (SAP) and 56 patients with acute coronary syndrome (ACS) including 29 with unstable angina pectoris (UAP) and 27 with acute myocardial infarction (AMI) were enrolled in this study. Serum CD44mRNA levels on the surface of PBMC were measured by real-time PT-PCR and were relatively quantified by β-actin as internal standard. RESULTS: The levels of CD44 mRNA in surface of PBMC in UAP patients and AMI patients were both higher than those in patients with SAP and in control group (P<0.05). The levels of CD44 mRNA in surface of PBMC in AMI patients were higher than those in patients with UAP (P<0.05). The levels of CD44 mRNA in surface of PBMC were not significantly different between SAP group and control group. CONCLUSION: The expression levels of CD44 in surface of PBMC were related to the CHD and the severity of the illness.