Transesophageal echocardiography (TEE) requires the introduction of a flexible probe into the oesophagus and therefore cannot be strictly considered to be non-invasive. This manipulation exposes the patient to complications which are benign in the large majority of cases. The authors report their experience in a prospective study analysing the failures and complications of TEE in the first 1,500 cases performed in their laboratory between May 1988 and May 1992, in mainly adult and ambulatory patients. The probe could not be introduced in 24 patients (1.6%), including 5 cases during the initial learning period. No serious complications were observed during of after TEE. Minor incidents were noted in 28 cases (1.9%) intolerance of the probe (12 cases), nausea and/or vomiting (4 cases), dyspnea (4 cases) due to tracheal intubation in 2 patients, laryngeal in 1 patient and to cardiac failure in 1 case. Pharyngeal haemorrhage (2 cases), atrial fibrillation (3 cases), vertigo (1 case), mandibular dislocation (1 case) and salivary hypersecretion affecting the quality of the imaging (1 case), were also observed. The investigation had to be interrupted prematurely in 12 cases (0.8%) usually because of intolerance of the probe. These results show that TEE is not dangerous in trained hands. Failure to introduce the probe is usually encountered during the learning period, which reinforces the need for apprenticeship in a teaching center. The safety of this technique, plus its considerable diagnostic value in many clinical indications, justify its present role in everyday cardiological practice.