The effectiveness of platelet concentrate transfusion depends on such variables as blood bag material, donor--recipient compatibility, and time elapsed between donation and transfusion. To study the latter a corrected thrombocyte increment for recovery in the recipients was evaluated with 108 platelet transfusions in 31 patients. In 83 treatment programs, the mean recovery at the one-hour post-transfusion time point was 8.6 X 10(9) platelets/l with fresh platelets and 5.9 X 10(9) platelets/l with stored platelets. Significantly better recovery was achieved with freshly prepared platelet over the total of platelet concentrates stored for up to 96 hours; however, if the recoveries in different patient groups given stored platelets were considered separately in terms of storage times of up to 48 h or 48-96 h, the good recovery with fresh platelets was significantly better only when compared to the older (p = 0.034) but not to the younger group of stored platelets. In patients with signs indicating enhanced platelet destruction (fever, splenomegaly, disseminated intravascular coagulation) the transfusion with fresh platelet concentrates gave a significantly better recovery compared to stored platelet concentrates (p = 0.028), whereas in the absence of such signs the recovery produced by fresh concentrates was not significantly higher than with stored concentrates. These findings may be relevant for the logistics in blood banking.