In eight patients with terminal renal insufficiency treated with repeated haemodialyses (group I) and six patients treated with intermittent peritoneal dialysis (group II), the effect was studied of treatment with r-HuEPO on the platelet count and activity. In the studied patients the following was determined: platelet count, ADP-induced aggregation, circulating aggregates, and the third (PF3) and fourth (PF4) platelet factors. The studies were performed before the introduction of r-HuEPO and during the treatment--after achieving of haematocrit increase in the patients to 30%. No significant increase was observed of platelet count or activity. In none of the studied patients the development of thrombotic complications was observed with haematocrit increase to 30%. In both studied groups during the treatment with r-HuEPO a significant increase was found of haemoglobin concentration, red blood cell count, and haematocrit value in relation to the values before starting the treatment.