Our aim was to assess echocardiographic parameters and the effort blood pressure of 50 children of hypertensives with respect to 50 children of normotensives. Systolic and diastolic blood pressures at rest were comparable between the two groups. Left ventricular mass index (LVMI), interventricular septum and posterior wall thicknesses were higher in children of hypertensives (P less than 0.01). Systolic blood pressure was higher in children of hypertensives at maximal effort until 5 min of recovery (P less than 0.01). Similarly, diastolic blood pressure was higher at 1 and 2 min of recovery (P less than 0.01). Direct correlations of mean diastolic wall thickness (r = 0.39, P less than 0.01) and LVMI (r = 0.33, P less than 0.05) with percentage effort systolic blood pressure increases were found in children of hypertensives but not in children of normotensives. In conclusion, we confirmed early cardiac alterations and a tendency for effort hypertension in children of hypertensives. The relationship between these data could be explained either by effort systolic overload or by a common response to an increased adrenergic stimulus.