The inhibition of glycolysis by an inhibitor of glucose utilization isolated from urine of the uremic subjects reflects in: (1) decreased platelet aggregation induced by adenosine diphosphate, adrenaline, or collagen, respectively; (2) decreased platelet factor 4 release induced by the same inductors; (3) decreased availability of platelet factor 3, and (4) inhibition of retraction of reptilase clot. It is concluded that the inhibition of glycolysis by ‘inhibitor of glucose utilization’ contributes to the functional changes of platelets and thus to the alteration of hemostasis in uremic patie