This study evaluated a newly developed polyolefin bag, which has a 50%/m2 higher oxygen permeability to extend the shelf-life of platelets. Single-donor aphaeresis platelets were pooled, separated equally into two bags, PO-80 (0·8 l capacity) and KBP-PO (1 l capacity) for control, and stored in plasma for up to 7 d. Platelet biochemical and functional parameters were monitored in bags containing high (4·2 × 1011/250 ml/bag, n = 9) and low (2·0 × 1011/200 ml/bag, n = 3) concentrations of platelets over the storage period. After 7 d of storage, the PO-80 bags containing high concentrations of platelets had a better pH (mean pH 6·74) than those stored in KBP-PO (pH 6·32, P < 0·01); none of the nine PO-80 bags with a high platelet concentration had a pH below 6·2, compared with four of nine controls (P < 0·05). Similarly, lactate values were 20·19 mmol/l and 28·09 mmol/l respectively (P < 0·05). Aerobic metabolism was maintained better with greater O2 consumption and less lactate generation in high-platelet concentration PO-80 bags than in the control bags. A significant difference was also found in pH, pCO2 and lactate levels between the two bags containing low concentrations of platelets during the 7-d period. The in vitro characteristics of platelets declined less over 7 d when stored in a higher oxygen permeable container than in a marketed bag.