Objective: Following corrective cardiac surgery in infants and children for congenital heart disease, a persistent low cardiac output refractory to conventional modes of treatment is associated with a mortality approaching 100%. We advocate the use of whole body hypothermia to reduce tissue oxygen demand and provide a degree of cellular protection against ischaemia allowing time for recovery. We describe our experience. Methods: Between July 1986 and December 1995, 1885 infants and children underwent surgery (operative mortality, 6%), 1302 requiring cardiopulmonary bypass. Fifty-seven patients had a persistent low cardiac output, impaired respiratory function, decreased urine output and acidosis despite maximal intensive care treatment. Cooling to 32-33 degrees C was therefore started using a thermostatically controlled water filled cooling blanket. Results: Following cooling, there was a fall in heart rate (P < 0.001), a rise in mean arterial pressure (P < 0.001) and a fall in mean atrial pressure (P < 0.001). Significant(P < 0.001) increases in pH and urine output were also recorded. Thirty-one (54%) of the 57 patients treated with cooling survived to leave hospital. No long-term sequelae have been noted in these patients. Conclusion: Induced hypothermia :is a useful salvage treatment, in children following corrective cardiac surgery when all conventional treatment has been tried and failed. (C) 1999 Elsevier Science B.V. All rights reserved.