The purpose of this study was to establish by means of the echocardiographic evaluation the normal values of ventricular diameters and volumes in horses, to compare these values with those published by other authors and to stablish if there is relationship between bodyweight and the variables studied. Ninety-nine horses, 296-546 kg body weight, cardiologically healthy and not trained were used. The measurements were made in guided M-mode, short axis images obtained from right parasternal window. Summary statistics for each dimension were determined including the range, mean, median, standard deviation, coefficient of variation and limit values. Least squares linear regression analysis was used to evaluate any relationship between measured variables and bodyweight. Differences between mean values were compared using a Student's t test. Repeatability for each dimension was assessed using a two-way analysis of variance. Statistical comparison with values of similar variables obtained by other author were made. The results were: Left ventricular diastolic diameter (LVDD) value: 10.31±1.17 cm, Left ventricular systolic diameter (LVSD) value: 6.16±0.98 cm; Left ventricular diastolic volume (LVDV) value: 600.50±156.63 ml and left ventricular systolic volume (LVSV) value: 200.66±77,71. Pearson's coefficient (r): LVDD: 0.4731, LVSD: 0.3171, LVDV: 0.412, LVSV: 0.3163. The horses were divided in two groups according to bodyweight (> 500 kg and < 500 kg). Significant differences in mean values of the studied variables were found
Keywords: Horse,echocardiography,ventricular diameters,ventricular volumes.