The aim of this study is to establish the incidence of serious morbidity and mortality associated with the placement of large-bore (18 to 20 F) percutaneous bypass cannulae for venovenous bypass (VVBP) during orthotopic liver transplantation (OLT). This technique has been reported to be rapid, simple, and safe. We reviewed the case notes of 312 patients who underwent OLT in our center using this technique. We describe 4 cases of serious morbidity (incidence, 1.28%) and 1 death (incidence, 0.32%) related directly to percutaneous placement of the bypass cannula. We conclude that percutaneous cannula placement for VVBP during OLT has the potential for life-threatening complications, and this must be considered when electing to use this technique. When percutaneous cannulae are to be used, we recommend the use of the right internal jugular vein for return cannulation and the use of ultrasound guidance, particularly in those patients in whom cannulation is predictably difficult.