The greatest role in the development of haemostasis disturbances in patients with chronic renale failure (CRF) is ascribed to the platelets. The purpose of the work was study of basic parameters of platelet haemostasis in patients with CRF treated both conservatively and subjected to repeated haemodialyses. A correlation was also sought between the degree of renal failure intensity and haemostasis disturbances. The subject of the study were 18 patients treated conservatively and 21 patients subjected to repeated haemodialyses. In the patients the following was determined: platelet count, bleeding time, aggregation by Breddin and Born methods, availability of platelet factor 3 (PF3), activity of platelet factor 4 (PF4), and also the concentrations of urea, creatinine, uric acid, albumins, sodium, potassium, calcium, haemoglobin, and red blood cell count, haematocrit, and endogenous creatinine clearance. In non-dialysed patients, in relation to the control group, unchanged platelet count was shown as well as prolonged bleeding time, increased aggregation assessed by the Breddin method but unchanged by the Born method, decreased PF3 availability and unchanged PF4 activity. Aggregation and bleeding time were correlated with the degree of uraemia progression assessed on the basis of biochemical parameters, while platelet count was correlated only with urea concentration. In haemodialysed patients unchanged platelet count was demonstrated as well as prolonged bleeding time, increased aggregation assessed by the Breddin method but simultaneously decreased in the Born method, increased PF3 availability and unchanged PF4 activity. In this group of patients the correlations were only found between bleeding time and haemoglobin concentration, haematocrit, and red blood cell count.(ABSTRACT TRUNCATED AT 250 WORDS)