Monitoring of platelet counts 1 hour after transfusion has become standard practice in most centers. In this study, platelet counts obtained 10 and 60 minutes after 48 platelet transfusions were compared. There was a close, linear relationship (r = 0.98) between these values over a wide range of posttransfusion counts, indicating rapid equilibration of transfused platelets. Ten-minute posttransfusion samples are easier to obtain and are convenient for both patients and medical staff.