BACKGROUND: In athlete's heart, functional and structural alteration are main features. We studied electrocardiograms(ECG's) and echocardiograms(UCG's) in soccer players before and after intensive training. METHODS: Fifteen soccer players with the mean age and career of 19.3 and 8.5 years,respectively,underwent intensive training for 5-5.5 months, which included running of 2 km daily during the last 2-2.5 months. Comparisons of ECG's and UCG's recorded before and after the training were made. RESULTS: The major abnormal finding in pre-training ECG's was high voltage being seen in 40% of the cases, and in UCG's left ventricular(LV) dilatation and/or hypertrophy or asymmetrical septal hypertrophy(ASH) were noted in approximately 80% of the cases. The incidences of these finding after the intensive training were essentially unchanged, and the mean of pre-and post-training fractional shortening(FS) and LV and left atrial dimensions were similar. The high voltage in ECG's showed no close correlation with LV dilatation or hypertrophy on UCG's. After the training, however, the mean values of the thickness of LV posterior wall and ventricular septum along with LV mass were significantly increased, and the right ventricular dimension was significantly decreased. CONCLUSIONS: The most frequent finding in ECG's and UCG's in soccer players, before and after intensive training,were high voltage, LV dilatation and /or hyperophy with or without ASH. The intensive training of 5-5.5 months duration caused no change in F8,but caused significant increase in the thickness of LV posterior wall and ventricular septum, and LV mass.