We have investigated resting electrocardiograms in 1,299 athletic students and 151 sedentary control subjects. ST elevations were more frequent and pronounced in athletes compared to controls, whereas there was no difference in ST depressions. Athletes with ST elevation above 2 mm were characterized by lower heart rate, increased PQ duration, increased indices of left, right and septal hypertrophy and T wave amplitude. Negative T waves in 3 of 6 precordial leads, V3-6, were found in 1.5% of athletes and 0.7% of controls, and in V5-6 in 0.4% of athletes and none of controls, the differences not being significant. Athletes had significantly more often a T wave axis between +30 and -180 degrees and less often a frontal T wave axis between +30 and +180 degrees. The mean QRS-T angle was significantly greater in athletes, and U waves were more prominent. Analyzing athletes with QTc below and above 0.430 s, we found an increased heart rate, QRS duration, ST depression and a more pronounced left QRS axis in the group with QTc above 0.430 s. There was a positive correlation between QTc and heart rate which indicates that the use of Bazett's formula leads to an underestimation of QTc at lower heart rates and to an overestimation at higher heart rates. Bazett's formula does not provide an adequate correction for heart rate and should be used with caution. Our finding of a prolonged QTc in athletes compared to control subjects in spite of lower heart rate in the athletic group demonstrates that a real QTc prolongation exists in athletes.