The aim of this study was to obtain reference values of cardiac dimensions and indices of function in Thoroughbred foals. In total 76 Thoroughbred foals (48 female, 28 male) were used in this study. The M-mode echocardiographic data of foals were obtained from birth until 24 months of age at 4 month intervals Most of the investigated parameters increased constantly with age except some fluctuations. Right ventricular internal diameter in diastole (RVIDd) was significantly higher in females than in males at the 4th month (P<0.05). On the other hand RVIDd tended to be higher in males than in females in the previous and next age groups (P<0.10). Left ventricular mass (LVM) was higher in males than in females at 8th month (P<0.05). In addition, left ventricular free wall thickness in systole (LVFWTs) values obtained at the 12th month in females and 20th month in males tended to be higher (P<0.10). Heart rate (HR) constantly decreased with age and tended to be higher in females than in males at the 8th month (P<0.10). As a conclusion the normal limits of echocardiographic parameters were found to be different in growing foals compared to that of adults and some gender based variations were determined. Therefore age and gender differences should be taken into account during interpretation of echocardiographic data.