Ventricular late potentials detected by signal averaging have a high predictive value for the origin of malignant ventricular tachyarrhythmias in patients with coronary artery disease. We examined 35 male sportsmen aged from 22 to 33 years. Clinical examination, ECG at rest, echocardiography and signal averaging were performed. In nine of the 35 sportsmen (26%) ventricular late potentials were detected. In a control group of 20 nonsportsmen none had late potentials. The nine sportsmen with late potentials all had electrocardiographical and echocardiographical signs of left-ventricular hypertrophy. Of the 26 sportsmen without ventricular late potentials five had left-ventricular hypertrophy. Ventricular late potentials are not rare in sportsmen. They seem always to appear together with left-ventricular hypertrophy.