Background: Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a risk predictor for cardiovascular diseases (CVD). Generally, plasma Lp-PLA2 was thought to be secreted by circulatory inflammatory cells. Lp-PLA2 mRNA expression of PBMC may also be a risk predictor. Methods: A total of 104 subjects angiographically verified ACS patients were enrolled, including 73 unstable angina pectoris (UAP) patients and 31 acute myocardial infarction (AMI) patients. Plasma lipids, Lp-PLA2 activity and Lp-PLA2 mass were measured. Lp-PLA2 mRNA expression of PBMC was relatively quantified by real-time fluorescence PCR. Results: Plasma Lp-PLA2 activity was increased in AMI patients compared to UAP patients (395.21±145.91 vs. 328.53±127.03 U/L, p=0.024). Lp-PLA2 mass of AMI patients was also higher than UAP patients (136.43±45.46 vs. 119.16±44.19 ng/mL, p=0.093), while PBMC mRNA expression was not statistically different [1.07 (0.74, 1.57) vs. 0.88(0.49, 1.99), p=0.453]. Comparing Lp-PLA2 mRNA by groups, Lp-PLA2 mRNA level was higher in male ACS patients and smoking ACS patients (p=0.008, p=0.048, respectively). Multivariate logistic regression analysis showed that Lp-PLA2 activity was an AMI risk predictor (OR=5.224, 95% CI 1.687-16.181, p=0.004), after smoking, systolic blood pressure, diabetes and hyperlipidemia were adjusted. Recurrent ACS patients were older (p=0.035), but they showed lower levels of Lp-PLA2 mass and Lp-PLA2 activity (p=0.014, p=0.045, respectively), compared to primary ACS patients. Conclusion: Smoking may be an important regulatory factor for Lp-PLA2 mRNA expression in PBMC. Among three Lp-PLA2 indexes, Lp-PLA2 activity was the best marker indicating AMI risk, while Lp-PLA2 mass maybe play better role as a predictor in avoiding ACS recurrence.