Introduction: RBC concentrates are the most important product in the transfusion activities. They are used to treat anemia, surgical and critically ill patients. Preserving function and quality of these products is one of the conditions for a successful transfusion therapy. Objective: The purpose of this study was to determine the biochemical and hematological changes that occur during storage of packed red blood cells in optimal conditions Materials and Methods: In ten packed red blood cells produced by standardized procedure we examined hematological (E, Hct, Hb, MCV, MCH and MCHC) and biochemical (AST, LDH, Na, K, Cl and pH) parameters on the first and 35th day of storage. In this purpose we used Advia 2102 hematology analyzer, biochemistry analyzer Beckman Coulter AU680 and RapidLab 1265 system for measuring pH. Statistical analysis was performed by Microsoft Excel 2007 program support. Results: During the storage of packed red blood cells number of erythrocytes, hemoglobin concentration and MCH were not significantly changed. Hct and MCV were slightly increased while the MCHC on the 35th day of storage was lowered. On the last day of concentrate storage AST, LDH and K were significantly increased. It was also observed a reduction of the pH value, Na and Cl. Conclusion: The most significant changes in the storage period erythrocyte blood products show in increasing concentrations of K, LDH and decreasing of pH. This is an important finding that must be considered in the treatment of patients with erythrocyte concentrates at the end of the storage period.