Failure of ductal closure is common in extremely low birth weight infants with significant postnatal morbidities from both pulmonary overcirculation (i.e. chronic lung disease) and/or systemic hypoperfusion (i.e. necrotizing enterocolitis). Early clinical signs of a hemodymanically significant ductus may be non-specific (i.e. hypotension, increasing ventilator requirements, metabolic acidosis) necessitating early screening by echocardiography. Cyclooxygenase inhibitors remain the first-line treatment option. Indomethacin remains the most commonly used agent, despite comparable efficacy and reduced risk of adverse events with ibuprofen. Surgical intervention is recommended after failure of medical therapy, contraindications to medical treatment or fulminating duct-related cardiorespiratory deterioration. Wherever possible, surgical intervention in ELBW infants should be avoided in the first week of life due to the potential risks of ischemia-reperfusion cerebral hemorrhage. The postoperative course is often complicated by left ventricular failure, pulmonary edema, and/or hemodynamic instability requiring close monitoring and physiologically relevant therapeutic interventions.