Between May 1974 and March 1989, 155 patients with double-inlet left ventricle had the Fontan procedure performed at the Mayo Clinic. Age at operation ranged from nearly 2 to 41 years (median 10). The operative mortality rate from 1974 through 1980 (39 patients) was 21%, but from 1981 through 1989 (116 patients) it was reduced to 9%. The 17 late deaths were secondary to reoperation (n = 8), progressive myocardial failure (n = 5), sudden arrhythmia (n = 3) and bleeding varices (n = 1). Neither operative nor late mortality rate was significantly related to age at operation. At follow-up of 6 months to 11 years (mean 4.9 years) in 111 patients, 88% were in good or excellent condition and 12% were in fair or poor condition. The Fontan operation can be performed with a mortality risk of less than 10% in properly selected patients with double-inlet left ventricle. Late results are encouraging when contrasted with the clinical course of patients before this operative approach was utilized.