Purpose: The primary purpose of this study was to determine the effects of resistance exercise training on early diastolic myocardial velocities (E') in an obese pediatric population. Methods: Twenty-three obese adolescents were selected to participate in either a resistance-based training program (RT; n = 13,12.2 +/- 0.4 yr, body mass index [BMI] = 32.5 +/- 1.9 kg.m(-2)) or a nonexercise control intervention (n = 10, 13.6 +/- 0.7 yr, BMI = 30.2 +/- 2.6 kg.m(-2)) for 8 wk. All subjects had repeated echocardiographic assessments to determine left ventricular (LV) geometry, early transmitral flow velocity (E), and E'. Results: LV mass and wall thicknesses did not significantly change with training or in controls. RT improved E' (11.9 +/- 0.5 to 13.3 +/- 0.5 cm.s(-1), P <0.01) in the presence of a decrease in E/E' (8.17 +/- 0.39 to 7.06 +/- 0.30 cm.s(-1), P <0.01), a marker of left atrial pressure. No changes were evident in the inactive control subjects. Conclusions: A supervised 8-wk RT exercise program improved early diastolic tissue velocity in obese children, independent of changes in LV morphology.