We evaluated cardiac function and the plasma levels of atrial (ANP) and brain (BNP) natriuretic peptides during bicycle (B) and hand-grip (HG) exercises in eight healthy males. Each test was preceded by a control protocol in resting conditions. Left ventricular (LV) function (echocardiography) was evaluated during both exercises. Atrial function was assessed only during HG. Plasma ANP significantly increased during B (+236%) and HG (+77%), while there was a significant trend towards higher plasma BNP levels during B (+41%) and HG (+30%) than during the corresponding control tests. Plasma ANP correlated with heart rate in both tests, with left atrial volume, pulmonary vein flow systolic fraction and mitral flow E/A ratio in HG; BNP in both test correlated with LV dimensions and function. These data suggest that during exercise the cardiac release of ANP and BNP is differently regulated and related to changes in left atrial and LV function, respectively.