The aim of this prospective study was to identify hemodynamic factors associated with two different types of polytetrafluroethylene (PTFE) AV grafts. The study was conducted on 46 hemodialysis patients over a 3-year period. The subjects were randomly assigned to one of two study groups: Group 1 patients (n = 24) underwent a brachiocephalic loop PTFE fistula; Group 2 patients (n = 22), a brachioaxillary PTFE fistula. Preoperatively, we recorded each individual's subclavian catheter history, hemodialysis frequency, and serum levels of parathormone (PTH), calcium (Ca)-phosphorus (P) product, homocysteine, protein C, and protein S. Doppler ultrasonography was used to evaluate vascular hemodynamic changes in the proximal and distal portions of the AV fistula at 48 hours and 1 week postoperatively. Group 1 showed a significantly greater number of ipsilateral subclavian catheter interventions prior to AV graft surgery than Group 2 (14 versus 7, respectively; P = .05; chi-square). The mean peak systolic velocity in the brachial artery in Group 1 was significantly higher than that in Group 2 at 1-week postoperatively (P = .04, paired t-test). The mean radial artery diameter in Group 1 was greater than that of Group 2 at 1 week postoperatively (P = .05, Student t-test). At 48 hours postoperatively the observed change in cephalic vein diameter in Group 1 was significantly greater than the change in axillary vein diameter in Group 2 (P = .08, paired t-test). Preoperatively, the mean serum protein C and protein S levels in Group 1 were higher than those in Group 2 (P = .03 and P = .04, respectively; Mann-Whitney U test). The total numbers of dialysis sessions per week in each group were significantly different (P = .001, chi-square). Six Group 1 patients exhibited graft thrombosis at 48 hours after AV graft surgery. None of the patients in Group 2 exhibited thrombosis at 48 hours or 1 week postoperatively. The results indicate that patients with brachiocephalic PTFE AV grafts show more significant changes in the cephalic vein and brachial artery than patients with brachioaxillary PTFE AV grafts. The findings also suggest that more ipsilateral subclavian catheter interventions and a higher weekly frequency of hemodialysis prior to AV graft surgery are risk factors for early thrombosis of PTFE AV grafts.