One hundred and twenty-five healthy, male top-level athletes were evaluated by echocardiography (Echo) and assigned to six groups according to the size of the left ventricular mass (L. V. Mass), calculated according to Devereux R. B. et al.: less than or equal to 200, 201-250, 251-300, 301-350, 351-400, or greater than 400 g. Echo evaluation of coronary artery (c.a.) proximal size was performed following the method described by Kalavathy et al. (J Am Coll cardiol 1986, 8, 1119-1124). Two of us separately conducted the measurement of the c.a. diameter at congruent to 1 cm from the respective aortic ostium on M-Mode tracings and 2-D end-diastolic frames. The inter-observer variability was lower for the M-Mode (4.2%) than 2D (9.3%) measurements: the correlation between A and B observers equals r = 0.867 for the right c.a., and r = 0.859 for the left main c.a.