In patients undergoing neurosurgical procedures at high risk for venous air embolism (VAE), the presence of a right-to-left shunt adds an additional risk for paradoxical air embolism (PAE). Although this is a rare complication, it can have devastating results. The most common form of right-to-left shunt is a patent foramen ovale (PFO), which can be detected by contrast echocardiography. This study evaluates the efficacy of preoperative precordial and intraoperative transesophageal echocardiography (TEE) to detect right-to-left shunting in patients undergoing neurosurgical procedures while in the sitting position. In 101 patients precordial contrast echocardiography was performed prior to surgery. The Valsalva maneuver was utilized as a provocative maneuver to facilitate demonstration of right-to-left shunting. Fifty-one of these patients also had intraoperative TEE monitoring. Right-to-left shunting was demonstrated in only six of the 101 patients examined. Of these, four were detected by TEE. This is less than the expected incidence based on the known incidence of PFO in the general population. The usefulness of preoperative ECHO as a screening test for PFO in patients undergoing neurosurgical procedures is limited, but when a PFO is found, valuable information is acquired to help manage these patients.