Abstract We report our experience from May 1985 to January 1991 with surgical complications and procedures performed in neonates on extracorporeal membrane oxygenation (ECMO) (218 venoarterial and 7 venovenous bypass). Eleven children older than 1 month were excluded. Total complications were 96 in 67 patients and included: bleeding (37), problems with initial cannula placement (17), thrombus formation (15), hemothorax, pneumothorax, or effusions (11), mechanical problems (11), and miscellaneous (5). Forty-eight procedures were performed in 37 patients while on ECMO. These were recannulation or reposition of cannulas (14), tube thoracostomy (11), cardiac surgery (6), cardiac catheterization (4), repair of congenital diaphragmatic hermia (5), thoracotomy (4), and others. Twenty-eight complications occurred in 15 of the 27 patients who died. Mortality rate was 12% for the entire group. Primary causes of death were hypoplastic lung (11), cardiac (8), sepsis (4), intraventricular hemorrhage (2), and pulmonary hypertension (2). No deaths were due solely to complications except for the two patients with intraventricular hemorrhage. Mortality in neonates who had complications while on ECMO was significantly higher ( P < .005) than in patients without complications. Hemorrhagic and thoracic complications were associated with higher mortality ( P < .001). Mortality was not affected by mechanical problems, thrombus formation, or catheterrelated problems. While on ECMO cardiac defects, diaphragmatic hernia, lobar emphysema, and other conditions can be safely corrected. The use of echocardiography to position the cannulas, better control of coagulation factors and improvement in equipment may ultimately decrease complications.