Cardiac surgery is infrequently but increasingly being used to repair congenital heart defects associated with trisomy 18. The clinical details of trisomy 18 patients undergoing cardiac surgery have rarely been reported. Seventeen patients with trisomy 18 and serious cardiac symptoms underwent cardiac surgery in our institution. Age at surgery ranged from 7 to 258 days (median, 66 days). One patient had an atrioventricular septal defect and coarctation of the aorta. The remaining patients had ventricular septal defects, including four patients with coarctation of the aorta. Fourteen patients had associated patent ductus arteriosus. Fourteen patients underwent palliative surgery without cardiopulmonary bypass, and four of these underwent a second-stage intracardiac repair. The other three patients underwent primary intracardiac repair. Postoperatively, 14 patients (82%) were discharged home with improved symptoms. Survival from birth ranged from 12 to 1384 days (median, 324 days). Eight patients survived longer than 1 year. Median postoperative survival was 179 days. Postoperative survival was significantly better after palliative surgery (0 to 1239 days; median, 257 days) than after primary intracardiac repair (1 to 179 days; median, 48 days). Only one patient died of heart failure, suggesting that cardiac surgery was effective in preventing heart failure-related death.