The change of erythrocytes count (ERc) as well as pH and osmosis of the erythrocytes mass (from National Institute of Hematology and Blood Transfusion) during storage period of 42 days in the presence of Mannitol with deffernt concentrations (0.3- 0.8 g/100 mL) was investigated. The ERc anh pH of ER mass was decrease graduanlly while the osmosis increased. Mannitol (0.5- 0.8 g/100 mL) show their ablility to maintain ERc, stabilize pH and osmosis in ER mass, but ony kept ERc (32 percent), pH (6.81) anh osmosis (345 mOsmol/Kg) at the end of 42 days storage period. M3 formu}ation (with Mannitol of 0.5 g/100 mL) was selected to be further studied in combination with other storage factors.