BACKGROUND: Cardiac syndrome X (CSX) has been associated with endothelial dysfunction and inflammation. We conducted a case-control study to evaluate the association between platelet and endothelial-derived microparticles (PMPs and EMPs), as specific quantitative plasma markers of endothelial dysfunction, and the presence of CSX.METHODS: The present study was conducted on 40 CSX patients and 19 healthy individuals. C-reactive protein (CRP), and hematological and biochemical parameters were evaluated. The MP concentration in platelet-poor plasma (PPP) was quantitatively determined through flow cytometry using specific anti-human CD31, CD41a, CD62E, and CD144antibodies.RESULTS: The mean platelet volume (MPV) and positive CRP rate (≥ 3.8 mg/l) were higher in patients compared to controls (P = 0.020 and P = 0.010, respectively). The CD62E+, CD144+, and CD31+41− EMPs, as well as CD41+ and CD31+CD41+ PMPs showed significant increase in CSX patients compared to controls (P < 0.050). There were direct correlations between the mean percentage of detected EMPs and PMPs as well as between their expression intensity; however, a reverse correlation was seen between the percentage of MPs and CD144and CD41. Moreover, the MP level was reversely associated with prothrombin time (PT) and partial thromboplastin time (PTT) values. Only CD31+CD41+ PMP was correlated with CRP.CONCLUSION: It seems that EMPs and PMPs increase in CSX, which may contribute to various processes involved in the development of this syndrome.