Introduction of the atrial baffle procedure (Mustard, Senning) more than 30 years ago has dramatically improved the prognosis of patients with transposition of the great arteries. However, a range of late complications can occur even in clinically asymptomatic patients including: superior and inferior limb obstruction, pulmonary venous obstruction, residual baffle-leakage, left ventricular outflow tract obstruction, tricuspid valve regurgitation, right ventricular dysfunction and postoperative dysrhythmia. As an increasing number of patients has reached adulthood an accurate noninvasive technique is needed for routine follow-up studies. In most patients transthoracic two-dimensional (2D) and Doppler echocardiography allows a complete investigation of postoperative hemodynamic abnormalities -- in particular assessment of atrial baffle function. In adult patients with restricted echo-windows transoesophageal echocardiography may provide a more detailed assessment of atrial baffle morphology and function; TEE seems to be superior compared to angiography and magnetic resonance imaging. Furthermore TEE is a reliable guiding and monitoring technique during interventional cardiac catheterization procedures such as balloon dilatation or stent implantation and allows further surveillance. Even if compared to other noninvasive diagnostic procedures, 2D and Doppler echocardiography (transthoracic/transoesophageal) are still the most important and accurate diagnostic methods for routine investigation of the postoperative anatomy and potential late complications in patients who underwent an atrial baffle procedure.