OBJECTIVE Indomethacin is accepted therapy for patent ductus arteriosus (PDA) in ELBW infants (<1000 g). We hypothesize that surgical ligation may provide comparatively superior outcomes in select ELBW infants. METHODS Predischarge outcomes of 298 ELBW infants with echocardiography-proven PDA were retrospectively compared by treatment provided: no treatment (group 1, n = 54), indomethacin (group 2, n = 140), ligation (group 3, n = 46), and ligation after indomethacin failure (group 4, n = 58). chi(2) and Wilcoxon rank sum tests were used to test for significance. Institutional review board approval was obtained (IRB/05-00395). RESULTS Group 3 had significantly lower gestational age (P < .001), birth weight (P = .006), and 5-minute Apgar scores (P = .03) compared with group 2. Group 3 and group 1 had a higher rate of pretreatment intraventricular hemorrhage (IVH) compared with group 2 (P < .001). By contrast, posttreatment complications including acute renal failure, necrotizing enterocolitis, thrombocytopenia, and IVH occurred more frequently in groups 2 (P = .004) and 4 (P = .001) compared with group 3. Survival was 57.7% in group 1 compared with groups 2, 3, and 4 (82.4%, 86.0%, and 92.7% respectively; P = .001). Preoperative conditions associated with nonsurvival include gestational age (P = .009), birth weight (P = .002), maternal preeclampsia (P = .015), 5-minute Apgar score (P = .013), and sepsis (P = .018). Posttreatment complications associated with nonsurvival include acute renal failure (P = .002), thrombocytopenia (P = .002), and necrotizing enterocolitis (P = .034). Survival was not influenced by any congenital comorbidity, pre- or posttreatment IVH, diameter of the PDA, or recurrence of the PDA after indomethacin therapy. CONCLUSIONS (1) Patent ductus arteriosis requires treatment in ELBW infants to maximize survival. (2) Indomethacin and surgical ligation permit equivalent survival in low-risk ELBW infants, but indomethacin results in a high failure and complication rate requiring operative salvage in a number of patients. (3) Surgical ligation permits survival of high-risk ELBW infants with a low complication rate and is preferable to indomethacin in ELBW infants with the above risk factors.