Cardiac output (CO) measurements by the three methods of dye dilution, pulsed Doppler echocardiography and thermodilution in horses under anesthetized conditions were compared. Although CO determined by the thermodilution method was slightly higher than those obtained by the other two methods, the measurements by all methods showed almost similar results. The coefficients of correlation between the dye dilution and thermodilution methods, the dye dilution and pulsed Doppler echocardiography methods, and the thermodilution and pulsed Doppler echocardiography methods were 0.87, 0.89, and 0.88, respectively (P < 0.01). These results indicate that pulsed Doppler echocardiography and thermodilution methods could be no less useful than the traditional dye dilution method for evaluating of CO in horses. The pulsed Doppler echocardiography method may offer some advantage over other two methods; it is non-invasive and enables continuous measurement of CO.