Activation of vascular endothelium and blood cells can result in the formation of microparticles (MPs), which are membrane vesicles with a diameter< 1 μm which can play a pathogenetic role in a variety of infectious and other diseases. In this study, we validated a modified quantitative method called “flow rate based calibration”, to measure circulating MPs in plasma of healthy subjects and malaria patients using FACSCalibur flow cytometry. MPs counts obtained from “flow rate based calibration” correlated closely with the standard method (R2= 0.9, p= 0.001). The median (range) number of MPs in healthy subjects was 163/μl (81-375/μl). We demonstrated a flow rate based calibration for the quantitation of MPs in P. falciparum malaria-infected patients. The median (range) number of MPs was 2,051/μl (222-6,432/μl), n= 28 in patients with falciparum malaria. The number of MPs in plasma from patients with severe falciparum malaria was significantly higher than in uncomplicated falciparum malaria (2,567/μl (366-6,432/μl), n= 18 versus [1,947/μl (222-4,107/μl), n= 10, p< 0.01]. Cellular origin of MPs in malaria patients were mainly derived from red blood cells (35%), platelets (10%), and endothelial cells (5%). There was no significant correlation between the total number of MPs and parasitemia. Flow rate based calibration is a simple, reliable, reproducible method and more affordable to quantitate MPs. inherited from their parental cells. They form a heterogeneous population but are defined by their size of less than 1 μm in diameter and the presence of phosphatidylserine (PS) on the vesicle surface (Combes et al, 1999; VanWijk et al, 2003). A variety of pathological conditions generate MPs, such as cardiovascular disease (VanWijk et al, 2003), idiopathic thrombocytopenic purpura (Jy et al, 1992), and thalassemia (Pattanapanyasat et al, 2004, 2007). MPs also have pathophysiological relevance through their interaction with neighboring or remote cells. Research on this topic