Between April 1985 and December 1989, outpatient transoesophageal echocardiography was performed in 133 adolescent and adult patients (14% of all outpatient transoesophageal studies) (age range 11-78 years; weight 30-95 kg) to determine the value of this technique both in establishing the primary diagnosis (62 patients) and in the post-surgical follow up (71 patients) of congenital heart disease. The results were correlated with the findings of precordial echocardiography, catheterization and surgical inspection. Clear advantages of transoesophageal imaging over precordial imaging include: (1) direct identification of atrial appendage morphology in all patients; (2) delineation of systemic and pulmonary venous connections; (3) atrial baffle function (eight patients); (4) better evaluation of the Fontan-type circulation (five patients); (5) improved morphologic assessment of the atrioventricular junction and valves (29 patients); (6) definition of subaortic obstruction (18 patients); and (7) definition of ascending aortic morphology in Marfan's syndrome and supravalvar aortic stenosis (13 patients). The problems encountered with transoesophageal imaging include: (1) limited imaging planes; (2) poor visualization of specific intracardiac regions (antero-apical trabecular septum, right ventricular outflow tract); (3) flow masking behind implanted intracardiac prosthetic material.