The present examination of the hearts of 59 horses of different ages and sex, shows gross- and microscopic anatomical dates. The hearts of 25 male and 29 female horses were examined in cardiomyocyte cross diameter, number of myocytes, number of myocyte- and non-myocyte- nuclei, number of capillaries in mm2, and cross diameter of capillaries in the left and right ventricular wall. The gross- and microscopic anatomical dates showed no age- or sex specific differences in the adult horses. Some correlations were found between microscopic parameters. The myocyte- cross diameter was significant larger in the left than in the right ventricular wall. Differences were also found in the number of myocytes and capillary- myocyte- relation. There were no significant differences between the left and right ventricular wall in following parameters: number of myocyte- and non- myocyte- nuclei, number of capillaries and composition of the ventricular wall. There is a positive correlation between the number of myocyte- and non- myocyte- nuclei. The positive correlation between the number of myocytes and capillaries can be confirmed for the horses.