Introduction. Metabolic syndrome (MS) is a cluster of distinct metabolic alterations with an increased cardiovascular risk. Peroxisome Proliferator-Activated Receptor - Alpha (PPARα), member of the nuclear receptor superfamily of transcription factors, is critically involved in the management of lipid metabolism during homeostasis or inflammatory stresses in various cell types and represents one of the therapeutic targets in MS. We analysed the PPARα expression in leukocytes of pacients with MS, in order to address PPARα involvement in these group of diseases. Material and method. Our study included 57 adult patients recruited under informed voluntary consent, investigated in order to establish whether they present MS, according to International Diabetes Federation (IDF) European guidelines and grouped in 2 lots: the MS Lot (26 patients) and control group, non-MS Lot (31 subjects). Common clinical and laboratory parameters targeted in MS evaluation were determined for all the studied cases. The expression levels of 2 molecules, PPARα and CD36 were evaluated in various circulating leukocyte populations of these patients by an optimized flow cytometry method. Statistic analysis clarifying the significance of value differences for various parameters measured was performed under SPSS and simple statistical tests (Pearson, t-Student, Chi -test). Results and discussion. The fluorescence staining for PPARα were significantly dimmer when comparing the cellular expression in eosinophils (p<0.05) of MS versus the Control group of subjects. Conclusions: Our study is the first to show that circulating eosinophils display significantly reduced PPARα protein expression in MS patients. The differences in key molecule expression in circulating leukocytes (like PPAR species, CD36, and other) might be evocatory for the endothelial dysfunction and obesity and might be of use in the therapeutic decision.