Echocardiographic determination of left ventricular mass index (LVMI) is shown to be valuable in the assessment of cardiovascular risk. Determination of left ventricular geometry, including concentric remodeling, provides additional prognostic information. In isolated systolic hypertension (ISH), the few echocardiographic studies available show an increased LVMI, but criteria and patient populations differ. No comparison with diastolic hypertension (DH) has been made, nor has left ventricular geometry (with concentric remodeling) been evaluated. We compared both LVMI and left ventricular geometry of newly diagnosed ISH subjects with normotensive and DH subjects, all previously untreated and from the same population. The echocardiographic LVMI of 97 previously untreated ISH subjects (4 x systolic pressure > or = 160 mm Hg, diastolic pressure < 95 mm Hg) was clearly elevated compared with values in age- and sex-matched normotensive subjects (98 and 71 g/m2, respectively; P < .001). The geometric pattern was abnormal in most ISH subjects, with a high prevalence (43%) of concentric remodeling. Both LVMI and left ventricular geometry of ISH subjects did not differ significantly from values in DH subjects (LVMI, 92 g/m2; concentric remodeling, 56%). Sex differences in LV geometry in ISH were present only with the Framingham criteria, not with the Koren criteria. This study shows a high prevalence of concentric remodeling in elderly individuals with previously untreated ISH. The increase of LVMI and abnormality in left ventricular geometry are comparable with those in DH subjects, further defining the place of ISH as a cardiovascular risk factor in the elderly. Whether there are sex differences in cardiac adaptation in ISH and whether the geometric classification can be used to adjust treatment remain to be investigated.