The detection of shunts at the atrial level is important, and a reliable means of diagnosis is required. Precordial contrast echocardiography is usually performed to detect such shunts. To investigate the advantages of transesophageal echocardiographic techniques, we studied 167 consecutive patients with both precordial and transesophageal echocardiography, using two-dimensional imaging with contrast techniques (with and without a Valsalva maneuver) and color flow mapping. A patent foramen ovale was diagnosed in 31 patients, an atrial septal defect in 11 (7 with bidirectional shunts), and a pulmonary arteriovenous fistula in 3 patients. All right-to-left shunts were detected with transesophageal contrast echocardiography. With these results used as the gold standard, the sensitivity of combined precordial techniques was 37% and that of transesophageal color flow mapping 46%. All left-to-right shunts were detected by transesophageal color flow mapping. With these results used as the gold standard, the sensitivities of both precordial color flow mapping and a transesophageal negative right atrial contrast study were 27%. We conclude that transesophageal contrast echocardiography is the echocardiographic method of choice for the detection of a right-to-left shunt at the atrial level, which cannot be excluded by negative results on precordial study or on transesophageal color flow map study. A left-to-right shunt at this level is best detected by transesophageal color flow mapping.