Cardiac output is considered the ultimate expression of cardiovascular performance. For the purpose to research validty of noninvasive cardiac output measured by thoracic electrical bioimpedance (TEB), 10 coronary artery patients ages ranged 43 to 62 (mean: 56) were inculuded into study. Simultaneous cardiac output measurements was done by using thoracic electrical bioimpedance and thermodilution at the induction, after opening of thorax and postoperative hours 1, 6 and 24. Results; induction of anesthesy; CO_TD: 4.3 ±1.2 L/min, CO_TEB: 4.4 ± 1.9 L/min, correlation coefficient r=0.949, p<0.001, after opening of thorax: CO_TD: 4.3+1.2 L/min, CO_TEB: 3.4±0.9 L/min, r=0.52 p<0.09, postoperative hour 1.; CO_TD: 5.6 ± 1.1 L/min, CO_TEB: 5.07 ± 1.4 L/min, r=0.73, p<0.05, and hour 6.; CO_TD: 5.4 ± 0.8 L/min, CO_TEB: 5.03 ± 1.4L/min, r=0.62, p<0.05, hour 24; CO_TD: 5.5 ± 1.3 L/ min, CO_TEB: 5.28 ± 1.3 L/min, r=0.89, p<0.01 were obtained. Correlation between TEB and thermodilution was observed at the induction and postoperative 24 hours,but could not be observed during the operation and postoperative 1 and 6 hours.