introduction: in recent years, haemodialysis lines sterilized using ethylene oxide have been replaced with lines sterilized using gamma irradiation, as several authors have proven that it is a more biocompatible method. on using lines sterilized by gamma irradiation, we observed that more clots were formed than with lines sterilized with ethylene oxide. aims: to observe whether there is a difference in the heparin doses used and in the formation of clots in the extracorporeal circuits sterilized using gamma irradiation and ethylene oxide. material and method: we carried out a quasi-experimental, longitudinal and prospective study using haemodialysis lines sterilized by gamma irradiation and by ethylene oxide on the same patient. on each patient, 12 consecutive haemodialysis sessions with each type of line were carried out. after each session, the blood loss in the arterial and venous chambers was evaluated, together with the heparin needs. results: the results obtained show that clot formation is higher in the lines sterilized using gamma irradiation and that the heparin dose was indeed modified, although it was not statistically significant. discussion: maintaining good anticoagulation of the extracorporeal circuit during dialysis makes it possible to: carry out a clinically satisfactory treatment during the time required, prevent estimated high losses and minimize the circulating heparin, reducing the side effects.