Fistula puncture site blood loss during and after hemodialysis was measured in 12 patients with end-stage renal disease. It was found to be 0.74 ± 0.32 ml per dialysis and 115.4 ± 49.9 ml per year in patients with Cimino A-V fistulas. Puncture site blood leak in patients with heterologous grafts was 1.77 ± 0.36 ml per dialysis and 276.1 ± 56.1 ml per year. The values obtained in this study are 5 to 10 folds less than those found in the original reports. Recent advances in dialytic technology are probably responsible for the observed improvement. The results also suggest that Cimino A-V fistulas are superior to the heterologous graft.