Anticoagulation of extracorporeal circuit still represents a major problem for hemodialysis units. Uraemic patients are at risk of hemorrhages, so anticoagulant could increase such a risk. On the other hand clotting of extracorporeal circuit may complicate inadequate heparin administration or hemostatic activation by the foreign surfaces. In this article we propose a simple standard for heparin administration and monitoring which allows the theoretical best anticoagulation for extracorporeal circuit. Our data also indicate that the effect of our proposed schedule is not influenced by the type of membrane or dialyser used.