Primary neonatal repair of congenital heart defects offers a number of potential advantages over a two-stage approach, but the application of this principle has been limited by the perceived increased risk of neonatal repair. However, the patient with palliative CHD continues to suffer from secondary effects on the central nervous system, the pulmonary arteries, the airways, and the heart itself. Because these consequences have been increasingly recognized, we have undertaken primary repair of a variety of defects within the first months of life. From January 1983 through August 1988, 304 neonates with a critical congenital heart defect underwent primary repair with deep hypothermic circulatory arrest or low flow perfusion techniques. The total mortality rate was 11.8%. The largest number of patients had transposition of the great arteries--167 neonates--with a total hospital mortality of 8.9%. Aspects of preoperative evaluation and management, intraoperative care, including anesthesia and cardiopulmonary bypass, and deep hypothermia (with or without circulatory arrests), as well as postoperative management, are discussed. These data suggest that many forms of complex congenital heart defects may be successfully repaired during the neonatal period. Improved methods of preoperative resuscitation and postoperative care have contributed to these results. Follow-up hemodynamic and electrophysiologic studies have confirmed the advantages of early repair. Elective repair of the neonate with a complex congenital heart defect looms as a goal in the not-too-distant future.