Platelet dysfunction and prolonged bleeding have been seen in man when glucose polymer solutions, such as dextran, are used to volume replacement. Hydroxyethyl starch (HES) is a glucose polymer slightly different from dextran, which is used as a sedimenting agent in leukapheresis procedures. This controlled study was performed to evaluate the effect of HES on platelet function in centrifugation leukapheresis donors. Plateletpheresis using the same machines and techniques but without HES was the control. Platelet function was assessed by bleeding time, platelet count, adhesiveness to glass beads and aggregation to collagen, epinephrine and several concentrations of ADP, before and after the pheresis procedures. Except for a decrease in platelet count after both procedures, no other major changes in platelet function were seen. After one exposure in previously unpheresed donors, HES does not induce platelet dysfunction.