After evaluation of efficacy of a low molecular weight heparin (LMWH), enoxaparine (Lovenox), in patients on continuous hemodialysis without a particular known hemorrhagic risk, this same LMWH was administered during 493 dialysis sessions to 46 patients presenting various degrees of risk of hemorrhage. Lower doses of 0.5 mg/kg or 0.75 mg/kg as bolus injections were administered at the start of the 4 or 5 hourly session. Clotting in the extracorporeal circulation (ECC) was noted in 0.6% treatments, the product being effective in all other sessions. Only one case of bleeding can be imputed to the LMWH injected during hemodialysis (0.2% of sessions). Although an open trial, the superiority of enoxaparine both for antithrombotic activity in ECC, and its simple management, as well as the small number of hemorrhages noted, has led to the routine use of this method in all patients at hemorrhagic risk.