The effect of 30% Urografin on platelet aggregation induced by adenosine diphosphate (ADP), epinephrine, and arachidonic acid was examined. In vivo and in vitro experiments in 10 nondiabetic subjects and in vitro experiments in 7 diabetic-uremic patients showed a statistically significant decrease in platelet aggregation 20 minutes after in vitro incubation or in vivo infusion with Urografin. Urografin concentration was about 2.4-2.5%. The possibility of bleeding induced by contrast media and the connection with acute renal failure in diabetic-uremic patients are discussed.