Abstract.Platelet concentrates (PC), prepared by platelet apheresis, were stored in four different types of blood bags. One of the bags, manufactured with a thinner PVC film than previously, was tested in three different bag volumes. From 25 donors a total number of 99 PC were prepared. Platelet numbers varied from 20 to 140 times 109platelets per bag. The cell count, pH, pO2, pCO2and lactate were determined initially and on days 1,3 and 5 of storage. In a separate test, the oxygen diffusion capacity of the bags was determined by oxidation of sodium sulfite in the presence of cobaltous chloride. The oxygen diffusion capacity found was 16 (PL 732, 300 ml), 13.5 (Teruflexa 800 ml), 11.5 (PL 1240, 400 ml), 10.6 (Teruflexa 600 ml), 9 (Teruflexa 400 ml) and 4 (PL 146, 300 ml) umol O2/h, respectively. For each bag type, the minimum and maximum platelet number stored with maintained pH levels (6.9–7.4) was defined. The maximum platelet number stored with maintained aerobic metabolism, correlated to the oxygen diffusion capacity of the bag, r = 0.998, p<0.001, n = 6; thus the maximum platelet number successfully stored for 5 days in each container can be predicted by determination of the oxygen diffusion capacity. In PC with a low platelet yield, pH values above 7.4 were observed after 1 and 3 days. When the results are compared with platelet yield data from routine blood banking, the optimal bags for platelet storage can be chosen. These conclusions must be further investigated in studies in viv