AIM: Left ventricular hypertrophy itself is one of the risk factors predicting cardiovascular mortality. In these groups of patients, sudden death risk related with ventricular arrhytmias is increased. Various methods are being used to determine arrhytmias and signal averaged electrocardiography is one of those methods. In this study our aim was to evaluate late potential frequency in sportsmen with left ventricular hypertrophy. METHOD: 32 healthy sportsmen, performing heavy sports, (age, 26+5 year) were included in our study. Control group consisted of 28 healthy person with the similar age (age27+6 year). Echocardiography, holler monitorization and signal averaged electrocardiography data were obtained. RESULTS: In the sportsmen and control groups values were QRSd: 108±9 msec, 92 ±8 msec (p<0.001); RMS40: 43±12 &micro; V, 55±10 &micro;V (p>0.05); LAS 40: 32±9 msec, 26±10 msec (p>0.05); GP (%): %3, %0 (p>0.05) respectively. Ventricular extrasyslole was seen in two subjects of sportsmen group. And supraventricular extrasystole was present in one person of control group CONCLUSION: In this small group of sportsmen, who have the diagnosis of left ventricular hypertrophy, we found that late potential positivity was in normal limits But, when compared with the control group, ORSd was significantly increased in sportsmen group. The most frequent cause of sudden death in sportsmen is unrecognized heart disease. Thus, these groups of sportsmen should be controlled periodically. We think that studies with larger sportsmen group should be performed to support the results of our study.