Abstract： Ten kidney xenograftings were performed in dog to pig combination.Hemorrheological parameters were detected respectively before transplantation,at the hyperacute rejection and at 10～15 minutes after the removal of the rejected kidneys.The results showed that platelet aggregation increased significantly in hyperacute rejection.Platelet and fibrinogen decreased signifieantly and the platelet aggregation recovered at 10～15 minutes after rejected kidneys were removed.It is indicated that the platelet and fibrinogen participate in the hyperacute xenograft rejection,and that platelet aggregation may provide a voluable and sensitive assay for hyperacute xenograft rejection.