Dialysis efficiency, platelet and leukocyte counts, as well as malonyldialdehyde (MDA) level and lactate dehydrogenase (LDH) activity in serum were assessed in 10 patients (8 males, 2 females, aged 28-58 years) treated with repeated haemodialysis due to terminal renal failure. Patients were examined twice: during a 4-hour haemodialysis in the presence of heparin as the anticoagulant, and a week later in the course of another haemodialysis combined with infusion of heparin and prostacyclin. Statistically significant lower level of urea at the end of dialysis and significantly higher urea clearance were found during haemodialysis with prostacyclin-heparin infusion in comparison with infusion of heparin alone. As compared with the initial values obtained prior to dialysis, neutropenia and thrombocytopenia were observed during haemodialysis with heparin alone but the counts remained generally unaltered when both prostacyclin and heparin were administered. During and after haemodialysis with heparin and prostacyclin both MDA level and LDH activity were lower than in case of haemodialysis with heparin alone.