We reviewed 103 cases of isolated complete atrioventricular septal defect. These cases represented 4.4% of the cases of congenital heart disease diagnosed in our hospital by catheterisation and angiography during 1971-88. Most children (n = 76) had Down's syndrome. Banding of the pulmonary artery was performed in seven cases and complete repair in 67 cases. In the period 1971-82 the complete correction was performed at a mean age of 23 months with a surgical mortality of 88.8%. In the period 1983-8 the mean age at complete correction was 13 months, the mortality 43.2%, and the five year actuarial survival was 46.8%. The 22 patients that survived after complete correction were in functional classes I and II of the New York Heart Association classification. After a mean follow up of 10 years only eight (36%) of the 22 who were followed up and treated medically survived; all had developed pulmonary vascular obstructive disease and were in functional classes III or IV. Our findings stress the importance of early complete surgical repair.