Background: The echocardiographic contrast agent Optison may be useful in patients undergoing cardiac surgery. This study investigates its effects on hemodynamics, cardiac performance, and oxygenation in this group of patients. Methods: Parameters of hemodynamic stability, cardiac performance, and oxygenation were measured in 57 patients by transesophageal echocardiography, electrocardiography, invasive arterial blood pressure and central venous pressure monitoring, capnography, pulsoximetry, and pulmonary artery catheter before and 5 and 10 minutes after an intravenous bolus of 0.3 mL of Optison. Results: No statistically significant differences in ST-segment changes, heart rate, arterial and central venous pressure, peripheral oxygen saturation, cardiac index, left ventricular ejection fraction, and regional wall motion were seen 5 and 10 minutes after injection of Optison compared with baseline parameters. Conclusions: Optison did not cause clinically important changes in parameters of hemodynamic stability, cardiac performance, and oxygenation in our patients. The intraoperative use of intravenous Optison appears to be safe in patients undergoing cardiac surgery, including in the use of cardiopulmonary bypass. (J Am Soc Echocardiogr 2001;14:595-600.)