Aim To evaluate pregnancy-associated plasma protein A(PAPP-A) as an early sensitive and specific marker indicating the instability of atherosclerotic plaques in patients with acute coronary syndromes(ACS). Methods In 20 patients with acute myocardial infarction(AMI),25 with unstable angina pectoris(UAP), 21 with stable angina pectoris(SAP),and 15 controls without coronary heart disease,the levels of PAPP-A were measured.Meanwhile,C-reactive protein(CRP),Interlukin-6(IL-6),the MB isoenzyme of creatine kinase(CK-MB) and cardian troponin Ⅰ(cTnⅠ) were examined. Results The PAPP-A,CRP and IL-6 levels were significantly higher in patients with AMI and UAP than in patients with SAP and controls(p<0.01).In patients with ACS(including AMI aand UAP),PAPP-A correlated with levels of CRP and IL-6,but not with markers of myocardial injury CK-MB and cTnⅠ. Conclusions PAPP-A levels are elevated in ACS.These increased levels may reflect the instability of atherosclerotic plaques in coronary artery,not representing specific mocardial necrosis.