The functional duration of vascular access in dialysis patients depends on the emergence of threatening complications. Discussions are constantly being held in an attempt to discover their causality and decrease their emergence. In 260 patients undergoing haemodialysis, we have studied the potential existence of a cause-and-effect relation between the emergence of complications in the vascular access and the applied type of arteriovenous (av.) anastomosis in the arteriovenous (AV) fistula. We have observed the incidence of all complications, both that of the thrombosis incidence as well as the primary and secondary fistula patency (survival). The complications – The examinees with the end-to-end anastomosis showed the incidence of 8.08%, 6.15% of the patients with the end-to-side anastomosis and 7.31% of the patients with the side-to-side anastomosis. The differences regarding incidences are statistically significant ( 2-test = 29.25; P=0.0001). Thrombosis – it has been found that thrombosis was the most frequent complication developing in 30.00 % patients with the end-to-end av. anastomosis, in 2.31% patients with end-to-side av. anastomosis and in 5.56% patients with side-to-side av. anastomosis. The difference between the highest and the lowest assessment is 27.69%, and it is statistically relevant ( 2-test = 33.920; P=0.0001). The »primary patency« (primary survival): within a 6-month interval following the establishment of vascular access, the first complications arose in 62.50% of patients with end-to-end av. anastomosis, 10.76% in those with end-to-side av. anastomosis and 18.88% in those with side-to-side av. anastomosis. The difference between the highest and the lowest assessment is 51.74%, which is statistically significant ( 2-test = 49.009; P=0.0001). The secondary patency: 24 months subsequent to the establishment of vascular access, the AV-fistula was still functional in 52.50% of the patients with end-to-end av. anastomosis, 89.23% in those with end-to-side av. anastomosis and 81.11% in those with side-to-side av. anastomosis. The difference between the highest and the lowest assessment is 36.73%, which is also statistically significant ( 2-test = 26.579; P=0.0001). According to our research, the end- -to-side type of av. anastomosis in vascular access provides better results both in relation to the duration as well as the maintenance of the functionality of the Av-fistula and in the lower incidence of the complications than the other types, and hence it shows a definite advantage.