Since there is no sufficient data regarding the development of the heart and maximal frequency running speed in national racehorses, the morphological and physiological capacity of the heart can be easily measured non-invasively by echocardiography. The main goal in selecting a racehorse is to select one that will show above-average athletic potential in its future racing life. The horses participating in our study were healthy and of different genders. The horses were examined in their shelters using an Esaote AU5 brand Color Doppler echocardiography device with a 10 mHz probe. Standard echocardiographic evaluation of horses was performed using two-dimensional (2D) mode, M-mode and Doppler echocardiography methods from 5 different windows, parasternal and apical. Detailed echocardiography was performed on the left and right chest of the horses included in the study. In the study, reference ranges of end-diastolic diameter, end-systolic diameter, interventricular septum (IVS) diastolic and end-systolic thicknesses, and posterior wall diastolic and end-systolic thickness diameters were established. Fractional shortening, ejection fraction, heart rate and ventricular masses were measured. Echocardiography showed that the horses' heart muscles were hypertrophic. Thickening was observed in the interventricular septum and posterior walls. In order to determine the athletic potential of national racehorses, field-oriented, non-invasive tests that do not disrupt the trainer's work routine are needed. One of these tests is the data obtained using the echocardiography technique on the morphological and physiological capacities of the heart in horses.