The electrocardiogram (EGG) of athletes reflects physiologic cardiovascular adaptations that occur in well-conditioned individuals. To more clearly define electrocardiographic changes seen in predominantly power-trained athletes, the ECGs of 289 apparently healthy professional football players were analyzed in detail. The players, aged 21 to 35 years, one-third of whom were black, had a mean body surface area of 2.24 m 2, a mean heart rate at rest of 56 ± 9 beats/ min (with 77% (223) having a rate of less than 60 beats/min), and a mean P axis of 30 ± 25 °. A wide QRS-T angle (>60 °) was present in 14% (41 players) of the group. The mean PR interval was 0.18 ± 0.02 second (>0.21 in 9% [26 players]). Although two-thirds of the players had a QRS duration of 0.10 second, only 1 had right bundle branch block and none had left bundle branch block. The sum of S in lead V 1 plus R in lead V 5 averaged 37 ± 9 mm, with 35% (101 players) demonstrating voltage criteria for left ventricular hypertrophy. The S + R value varied inversely with weight (r = −0.27, p < 0.002). The maximum T height in any lead had a mean of 8.6 ± 3 mm, with 22% (64 players) having a T height ≥11 mm. U waves were universally present. ST-T changes mimicking ischemia were noted in 39 of 289 players (13%), 22 (58%) of whom were black (p < 0.001). The maximal J-point elevation in any lead averaged 1.9 ± 0.9 mm. These findings confirm that the ECGs of power-trained athletes show changes similar to those of endurance-trained athletes. These changes most likely reflect the increased vagal tone and ventricular mass observed in conditioned athletes. Large body size masks the voltage changes expected with increased left ventricular mass. Ischemic-like ST-T-wave deviations were found predominantly in black athletes.