Thoracic Electrical Bioimpedance (TEB) is a method for measuring cardiac performance which is noninvasive, continuous, has minimal technical requirements, and no patient risk. We used a commercially available TEB device to measure cardiac output in patients with thermodilution catheters in place. We compared the cardiac output measurements for the two modalities. We also compared the average hospital cost for initial cardiac assessment using the two techniques. The mean difference between the two cardiac output measurements was small (0.23 +/- 0.56) and not affected by the magnitude of the cardiac output readings. There was a strong correlation between COTD and COTEB (r = 0.91) and the regression slope was 0.91 with a Y intercept of 0.76. Cost analysis demonstrated that the use of TEB was approximately $600 less than thermodilution. Thoracic electrical bioimpedance measurement of cardiac output may offer a valuable alternative to the invasive measurement of the thermodilution catheter.