Abstract Background: Platelet concentrates (PCs) with the imple-mentation of bacterial testing have a storage period of 7 days. It was reported that platelet function decreased gradually in vitro until the 5th or 7th day of storage. Pooled PCs (PPCs) are main-ly used in Europe and Canada and there is the possibility to use many PPCs with 7 days storage for transfusion in case of bleeding or massive transfusion. Aim of Study: The aim of this study is to test in vitro both storage conditions and function of platelet-rich plasma (PRP-PCs) during storage for 7 days to assess the function of the PCs for the possibility to extend the use of stored PCs up to 7 days and its use for therapeutic and massive platelets transfusion. Patients and Methods: In this study 18 PRP-PCs, were evaluated for chemical analysis by measuring pH, LDH pro-duction, and glucose consumption levels and platelet aggre-gation testing using adenosine diphosphate (ADP), collagen (COLL), and ristocetin (RIST) and epinephrine (EPI) on days 1,3,5, and 7 of storage of PCs. Results: The platelets yield was >5.58 x 1010 which indi-cates accurate platelet separation and storage. The metabolic parameters indicated stable storage conditions throughout the 7-day period. The chemical analysis showed that there is stable pH during all days of storage above 6.4. Aggregation respons-es of the PCs decreased gradually and significantly (p<0.001) starting from 1st day when compared with 3rd, 5th and 7th day. On the 7th day the platelets lost their response to EPI and ADP, while still maintaining a normal response to RIST and weak to COLL. Conclusion: There is a loss of some function on the 6-7th day of platelet storage which may indicate that it is suitable for prophylactic more than therapeutic transfusion. In order to pro-vide more clinical benefit to the patients with thrombocytopen-ic bleeding, the platelets should be less than 7 days of storage.