Between January 1, 1982 and January 1, 1988, 49 complete corrections of complete atrioventricular canal were performed in children aged from 4 months to 8 years. 41 were infants less than 2 years' old and 31 were less than one year old. In the last 35 patients the "composite double patch" technique was used, consisting of closure of the interventricular septal defect with a dacron patch, followed by closure of the ostium primum with a pericardial patch. The mitral cleft was left intact in the last 6 operations. The overall mortality rate was 35 p. 100 (17 patients). It was 23 p. 100 in infants under 1 year and 17 p. 100 in infants aged from 6 to 12 months at the time of surgery (p less than 0.01). Seven of the 35 children in whom the "composite double patch" technique was used died (20 p. 100). Only one early death was recorded among the last 15 children operated upon. Two reoperations were performed: one within one month of the first operation, the other 4 months later for residual mitral regurgitation with haemolysis. 32 children were followed up for periods of 2 months to 6 years, 10 of them for more than 3 years. Two late deaths occurred during the follow-up. Grade 2 or 3/4 residual regurgitation was found in 14 patients who have regular clinical and echocardiographic examinations.(ABSTRACT TRUNCATED AT 250 WORDS)