OBJECTIVE--To report recent experience of patients with complete atrioventricular septal defect and tetralogy of Fallot, with emphasis on anatomical features, diagnosis, and management. DESIGN--Case notes were reviewed and patients were assessed at follow up by clinical examination and cross sectional and Doppler echocardiography. SETTING--Tertiary cardiothoracic referral centre. PATIENTS--Between 1987 and 1992 13 patients with atrioventricular septal defect and tetralogy of Fallot (12 with concordant and one with double outlet ventriculoarterial connections) underwent surgery; 10 underwent complete intracardiac repair. 11 patients had Down's syndrome. The complete diagnosis was established preoperatively by cross sectional echocardiography in all but one patient. A tri-leaflet left atrioventricular valve as seen in parasternal short axis views was the diagnostic feature of atrioventricular septal defect, with tetralogy of Fallot diagnosed from the presence of anterocephalad deviation of the outlet septum producing subvalvar pulmonary stenosis as seen in subcostal right anterior oblique views. INTERVENTIONS--Total correction consisted of closure of the atrioventricular septal defect by a combined right atrial and ventricular approach, reconstruction of the atrioventricular valves, and relief of the obstruction within the right ventricular outflow tract. Separate patches were used to close the atrial and ventricular septal defects. Modified Blalock-Taussig shunts were performed in three patients, who await intracardiac repair. Surgical correction was carried out at mean (range) age of 5 (2 to 15) years. MAIN OUTCOME MEASURES--Diagnostic methods, surgical results, and functional state after complete correction. RESULTS--The presence of an atrioventricular septal defect was missed preoperatively in one patient with tetralogy of Fallot. The characteristic goose neck deformity on the left ventriculogram was not present and the tri-leaflet nature of the left atrioventricular valve was not sought on echocardiography. Of the 10 patients who underwent complete repair, nine are alive and one died 34 days after operation with adult respiratory distress syndrome. Examination at necropsy showed an excellent surgical correction. Mean (range) follow up was 23 (8 to 48) months. All nine patients are alive and well (New York Heart Association Class 1). CONCLUSION--Accurate diagnosis and staged management with improved surgical techniques have lowered mortality of this complex combination of cardiac defects. The current policy of this group is to recommend a systemic to pulmonary arterial shunt procedure for symptomatic children younger than 2 years and total correction in older children.