Several strategies for pathogen reduction are being developed to reduce the risk of pathogen transmission associated with platelet transfusion. There is concern that these techniques could have a deleterious effect on platelet integrity and functions. We evaluated the impact of a new technology for pathogen reduction based on riboflavin + illumination at 6.2 and 12.3 J/ml (Mirasol PRT) on functional and biochemical characteristics of platelets. Platelet concentrates (PCs) obtained by apheresis (n=8) were treated with Mirasol PRT and then stored at 220 C. Modifications in major platelet glycoproteins (GPIb, GPIV, and GP IIbIIIa), adhesive ligands (vWF, Fg, and Fn), activation dependent antigens (P-selectin and LIMP), and apoptotic markers (Annexin V binding and factor Va) were analyzed by flow cytometry. Adhesive and cohesive functions of platelets in the concentrates were evaluated using well-established models with circulating human blood. Studies were performed the preparation day (day 0) and along storage (days 3 and 5) of PCs. Aliquots were taken for aerobic and anaerobic microbiologic cultures. No bacterial growth was observed. Exposure to PRT treatment results in very mild modifications in platelet counts. Levels of GPIb, GPIIb-IIIa and GPIV remained stable during storage in PCs treated with PRT 6.2J/ml and in the same range as those observed in non treated PCs. However, when PRT 12.3 J/ml was applied, levels of GPIb moderately decreased along days of storage 3 and 5. VWF, Fg, and factor Va did not modify their expression, neither by treatment nor by storage period. Fn appeared more elevated in all PRT samples when compared with non-treated samples. A progressive increase in P-selectin and LIMP expression and in Annexin V binding was observed during storage of PRT-treated PCs. Functional studies in perfusion models indicated that Mirasol PRT 6.2 J/ml treated platelets preserved adhesive and cohesive function to levels compatible with those observed in the respective control PCs. In conclusion, platelet function was well preserved in PCs treated with Mirasol PRT 6.2 J/ml and stored for 5 days.