BACKGROUND The detection or ruling out of a patent foramen ovale (PFO) can be determined noninvasively by contrast echocardiography (CE). The transesophageal technique is superior to the transthoracic technique regarding sensitivity, whereas the specificity of both methods is equally high. This prospective study shows the rational use of transesophageal CE for the detection of a PFO, in patients without cardiovascular disorders. METHODS 165 patients (92 female, 73 male, age 48 +/- 18 years) with planned neuro-surgery in a sitting position, underwent CE to rule out a PFO. If the CE was positive, an alternative position was selected in order to avoid a paradoxical air embolism. RESULTS Initially, a transthoracic CE was performed in all patients resulting in 21 patients (13%) being positive and 39 patients (24%) being negative by sufficient image quality. A transesophageal CE was performed in 96 of the remaining 105 patients (63%). Here, further 25 patients showed a positive CE in the sense of a PFO. The combined use of transthoracic and transesophageal CE revealed a PFO in 46 of 165 patients (28%). CONCLUSIONS The use of both, transthoracic and transesophageal CE is an efficient approach to the preoperative detection of a PFO in the sense of quality and economics. Depending upon the image quality, the use of a transesophageal examination could be avoided in one third of the cases.