Forty-nine patients who had received radiocephalic hemodialysis fistula construction were evaluated with duplex Doppler ultrasonography to characterize the Doppler indices of the feed radial arteries just proximal to the site of anastomosis. Forty-four patients had fistulas with good function, and 5 patients had fistulas with inadequate blood flow or thrombosis within 4 weeks after the operation. A preliminary study showed extensive variability in peak systolic velocity and end-diastolic velocity in the feed arteries. The resistive index dropped significantly 1 week after the operation and remained relatively constant over the following 5 weeks. In the success group, the mean resistive index measured 1 week after operation was 0.40+/-0.06. It was higher than that of the failure group (mean resistive index: 0.52+/-0.06). Among patients with well-functioning fistulas, diabetic patients had higher resistive indices than did non-diabetic patients (0.44+/-0.04 vs. 0.37+/-0.06). Our results suggest that a higher resistive index of the feed artery is closely related to early autogenous primary hemodialysis fistula failure.