The records of 100 consecutive patients undergoing transantral ligation of the internal maxillary artery (IMA) for epistaxis, including 15 patients who developed postoperative bleeding, were reviewed. Preoperative parameters predictive of surgical failure were advanced age, anemia, and a history of hypertension. The causes of postoperative epistaxis, as determined by surgical reexploration or angiography in 12 cases, included failure to identify the IMA in the pterygomaxillary space (6 cases), blood flow through partially closed clips on the IMA (2 cases), bleeding from posterior ethmoid arteries (2 cases), and revascularization of the nasal blood supply (2 cases). The incidence of surgical failure may be reduced by proper techniques of IMA identification and ligation.