Objectives The purpose of this study was to establish an electrocardiographic (ECG) profile in a biracial population of highly-trained American football players. Background Intense physical training can induce cardiac structural and functional changes (“athlete's heart”), including 12-lead ECG alterations. That race might play a role in determining ECG patterns has been suggested, although not studied in a large athletic population comparing black and white athletes. Methods Electrocardiographic analysis of 1,959 elite male athletes attending the National Football League Invitational Camp from 2000 to 2005 was performed. Subjects were classified by race and player position and judged free of structural heart disease. Results Abnormal ECG patterns were present in 480 (25%) athletes and were significantly more common among black players (n = 396; 30%) compared with white players (n = 78; 13%) or other races (n = 6; 15%) (p < 0.0001). Distinctly abnormal ECG patterns, suggestive of cardiac disease, were also more common in blacks (n = 76; 6%) than whites (n = 11; 2%) (p = 0.0005). In multivariable analysis, black race was an independent predictor of abnormal ECGs (risk ratio [RR] 2.03, 95% confidence interval [CI] 1.56 to 2.64, p < 0.0001), including patterns judged distinctly abnormal (RR 2.59, 95% CI 1.18 to 5.67, p = 0.02). Abnormal ECGs were also related to player position: most frequent in wide receivers (n = 91; 35%) and least common in quarterbacks (n = 16; 14%) and place kickers (n = 8; 11%). Echocardiograms, obtained in 203 athletes (10%), did not show structural cardiac abnormalities. Conclusions Electrocardiographic abnormalities were 2-fold more common in black than in white highly-trained male American football players, with race an independent determinant of ECG pattern. These findings have important implications for pre-participation cardiovascular screening of athletes with ECGs.