The disturbances of platelet function in end-stage renal failure varies in dialysed and non-dialysed patients. We examined some platelet function in 11 uremic patients treated conservatively (TC) and, again in the same patients, 3-month after the beginning of repeated hemodialysis treatment (HD). The blood samples were taken before hemodialysis. In TC patients normal platelet count, prolonged bleeding time, normal platelet aggregation, unchanged PF4 activity and decreased PF3 availability were shown, compared with control group. In HD patients also normal platelet count and prolonged bleeding time were noted, but increased platelet aggregation, increased PF4 activity and PF3 availability were observed, compared with control group and with TC patients. We conclude that in TC patients rather decreased platelet function was observed; after the beginning of hemodialysis treatment some platelet function became significantly enhanced, which suggests platelet activation. Moreover, in HD patients the disturbances of platelet function before dialysis were shown, then it is possible that platelet activation persists in interdialytic period.