Purpose: To evaluate platelet-related hemostasis during hemodialysis performed with five different anticoagulation methods. Methods: 31 chronic hemodialysis patients, 71% men, aged 57.5 +/- 17.4 years, participated in our prospective study. Platelet function analyzer PFA-100 closure time (collagen/epinephrine -CEPI, collagen/adenosine diphosphate -CADP) was measured before and after hemodialysis, which was performed consecutively with five different anticoagulation methods: full-dose unfractionated heparin (UFH) and low-molecular weight heparin (LMWH): 31 patients, regional citrate anticoagulation (RCA): 28 patients, low-dose heparin: 25 patients and "heparin-free" dialysis: 9 patients. The degree of clotting in the dialysis system was graded on a 5 point scale. Results: CEPI (mean SD, reference range 80-160 sec) before vs. after hemodialysis: UFH: 171.7 +/- 62.1 vs. 170.8 +/- 67.3; LMWH: 167.4 +/- 56.9 vs. 159.4 +/- 56.4; low-dose heparin: 175.3 +/- 69.0 vs. 183.1 +/- 60.5; RCA: 172.6 +/- 57.4 vs. 161.6 +/- 57.0; "heparin-free": 181.7 +/- 56.8 vs. 209.0 +/- 66.5; all differences nonsignificant. CADP (mean SD, reference range: 68-121 sec) before vs. after hemodialysis: UFH: 132.0 +/- 56.6 vs.146.3 +/- 68.4; LMWH: 132.4 +/- 57,0 vs. 123.1 +/- 50.8; low-dose heparin: 137.2 +/- 64.2 vs. 143.8 +/- 55.5; RCA: 140.7 +/- 48.2 vs. 132.9 +/- 48.1; "heparin-free": 137.1 +/- 68.0 vs.139.2 +/- 29.7; all differences nonsignificant. Before hemodialysis procedure CEPI was increased in 51.2% and CADP in 48.4% of the patients. The best dialysis system clotting score was found with UFH, LMWH and RCA. Conclusions: Platelet dysfunction was demonstrated in approximately half of the chronic hemodialysis patients and was not improved after hemodialysis, regardless of the anticoagulation regimen used.