Continuous arteriovenous hemofiltration requires continuous anticoagulation to prevent early hemofilter clotting. We used heparin given continuously in the arterial line of the extracorporeal circuit as anticoagulant in children with initially normal coagulation status, and heparin and/or prostacyclin in high-risk bleeding patients with preexisting coagulopathy. Heparin infusion enabled a mean running time of 22.2 ± 9.6 h, with the 0.1-m2 hemofilter and of 26.6 ± 4.7 h with the 0.25-m2 hemofilter. The mean filter running time with combined heparin/prostacyclin infusion was 31 ± 8.8 h. Prostacyclin as the sole anti-thrombotic agent provided good filter function only in 1 patient with preexisting coagulopathy. No adverse effects such as bleeding, thrombosis, or hypotension were observed.