Simultaneous assessment of left ventricular (LV) and right ventricular (RV) response to exercise is limited with the current imaging modalities. Magnetic resonance imaging (MRI) techniques are now under development that allow near real-time evaluation of biventricular function under physical stress. This approach may open new avenues to study heart function in response to exercise in health and disease. The aim of this study was to evaluate biventricular response to supine physical exercise using ultrafast MRI. Biventricular volumes and function were examined in 16 healthy volunteers (mean age 18 +/- 2 years) using an ultrafast MRI sequence at rest and during an exercise protocol on a MRI compatible bicycle ergometer. Exercise level was individualized at the workload corresponding to 60% of the maximal oxygen uptake. All subjects completed the exercise MRI examination, allowing functional evaluation. Stroke volume of both ventricles increased from rest to exercise (left ventricle, 89 +/- 14 ml vs 102 +/- 19 ml, p < 0.05; right ventricle, 88 +/- 14 ml vs 101 +/- 16 ml, p < 0.05). Ejection fraction also increased in both ventricles from rest to exercise (left ventricle, 63 +/- 6% vs 74 +/- 6%, p < 0.05; right ventricle, 61 +/- 6% vs 70 +/- 6%, p < 0.05). End-systolic volume of the left and right ventricles decreased from rest to exercise (left ventricle, -33 +/- 12%, p < 0.05; right ventricle, -25 +/- 12%, p < 0.05), whereas LV and RV end-diastolic volumes remained unchanged. The results fit well with current concepts of cardiac physiology, and therefore we conclude that ergometer-induced exercise MRI is a valid approach to assess physiologic changes in LV and RV function simultaneously.