The influence of an exercise training on anthropometric changes and cardiac dimensions was studied in 18 obese children (age 10 to 11 years). Eighteen obese children participated in a jogging program, 5 days/week, for 1 or 2 years and 15 normal weight children (age 10 to 11 years) in the control group participating in their regular physical education class. Anthropometric measurements, echocardiograms and electrocardiograms were obtained before and after the exercise programs. The weight, degree of obesity and resting heart rate had decreased after 1 year of the exercise training. Left ventricular end-diastolic dimension increased after 1 year of the exercise training. Left ventricular wall thickness did not change. The total voltage in SV1 + RV5 decreased after 3 months of the exercise training but returned to pre-training voltage after 1 year of training. There was no change after 2 years of training. In conclusion, 1 year of exercise in obese children decreased resting heart rate and increased left ventricular end-diastolic dimension and left ventricular mass.