Complex disturbances in hemostasis characterise chronic renal insufficiency. Defect of primary hemostasis is a common cause of bleeding complications. The hemodialysis procedure (HD), by itself, influences platelet function (the key part of primary hemostasis) which is compromised after the procedure. Many functional defects of thrombocytes have been described in end stage renal failure (ESRF) patients; one of them is adhesion defect where the pivotal role plays the complex of glycoprotein Ib (GP Ib) and IX. The aim of the study was to determine the extent of activation, reactivity of platelets and expression of GP Ib in ESRF patients. The flow cytometry method was used, and thrombin was used for stimulation of thrombocytes. Membrane expression of GP Ib and selectin P was assessed in 14 hemodialysed patients before and after stimulation with thrombin, before and after HD and in 10 healthy persons. The patient group had lower expression of GP Ib on resting platelets and significantly lower expression of selectin P after stimulation with thrombin when compared to the control group. After HD, thrombocytes had much lower expression of GP Ib; however there was no difference in expression of selectin P when compared to the state before HD. A lower reduction of GP Ib expression after stimulation with thrombin was observed after and before HD. On the basis of the results the following conclusions may be drawn: hemo-dialysed ESRF patients have lower expression of platelet GP Ib and reactivity of thrombocytes; the HD results in further depression in expression of GP Ib and reactivity of thrombocytes. It is plausible that nitric oxide (NO) released during HD modulates the expression of selectin P, but it remains to be confirmed.