Preliminary results of a review of sudden cardiac death in the adult with congenital heart disease were presented at the Canadian Adult Congenital Heart (CACH) Network meeting during the Canadian Cardiovascular Society's annual meeting in October 1994. Of 125 patients who were known to have died, sufficient details were available for 92 to determine the circumstance of death. Sudden death occurred in 23 patients (estimated incidence 5.3 per 1000 patients followed per year) at an average age of 33.5 +/- 11.9 years. Surgical procedures included intracardiac repair in 12, palliative procedures in only six and no cardiac surgery in six. Nine patients with sudden death had Eisenmenger syndrome. Right or left ventricular abnormalities were present in 15 of 21 patients with premorbid echocardiographic evaluation. A prior history of ventricular arrhythmia was available in only three patients. Sudden death is a significant cause of mortality in adults with congenital heart disease. Determination of risk factors will be an important aspect of the patient database under development by the CACH Network.