Platelets, which have an important role in hemostatic mechanisms and which were prepared by single and random methods were investigated to measure quantity, and aggregation response during 5 days of storage. The aggregation response and quantitative values of platelet concentrates (PCs), 60 of which were prepared by a single donor method and 62 by a random method were investigated during the 1st, 3rd, and 5th days of storage. The single donor platelets (SDP) were obtained by using the MCS Plus apheresis device and the random donor platelets (RDP) were obtained by two-phase centrifugation in the Heraeus 8500i centrifuge device (during the first phase, platelet rich plasma was obtained then platelet concentrate was obtained from this product) and were stored at 22 degreesC on a circular agitator. In addition, pH, PO2, PCO2, glucose and lactate values were measured in order to evaluate the effects of storage. The aggregation response was measured using adenosine diphosphate (ADP), epinephrine (EPN), collagen (COLL) and ristocetin (RIST). The cell count in mm(3) and the total cell count were also measured. The total cell counts and cells in mm(3) of the PCs which were prepared by the single donar method on the 1st, 3rd and 5th days, were: 3.11 x 10(11), 3.09 x 10(11), 3.07 x 10(11) and 292 x 10(3), 290 x 10(3), 289 x 10(3) and of those prepared by the random method were: 5.71 x 10(10), 5.69 x 10(10), 5.66 x 10(10) and 156 x 10(3), 153 x 10(3), 151 x 10(3). The mean aggregation responses of the PCs prepared by the two methods on the 1st, 3rd and 5th days, expressed as a 'X, were: ADP: 94.8-93.2, 81.6 78.7, 44.3-8.2; COLL: 91.7-89.6, 79.2-74.2, 29.8-11.1. EPN: 88.5-91.3, 64.2-62.7, 39.4-4.5 and RIST: 89.4-89.4, 76.5-73.6, 14.4-3.2. Other data related to platelet storage were obtained by measuring the pH, PO2, PCO2, glucose and lactate levels of the PCs. In our study, it was determined that in spite of the optimal storage conditions, the aggregation response of the PCs decreased significantly, whereas, the numerical values changed little during the storage period. (C) 2002 Elsevier Science Ltd. All rights reserved.