A cross-sectional study was conducted to compare the morphological and functional characteristics of the cardiovascular system among subgroups of hypertension defined by the JNC-VI recommendations. One hundred and sixteen subjects (normotensives and unmedicated hypertensives: 49+/-10 yr) were classified into 4 groups based on the criteria of JNC-VI: normotensive (NOR: n = 38), high-normal blood pressure (HN: n = 16), stage 1 hypertensive (SI: n = 28), and stage 2 to 3 hypertensive (SII-III: n = 34). Ultrasonographic examinations of the heart and carotid artery were performed in all subjects, and the following parameters were obtained: left ventricular mass index (LVMI), relative wall thickness at end-diastole (RWTd), cardiac diastolic function (A/E), common carotid artery diameter (CAD), intimal media thickness of the common carotid artery (IMT), and distensibility of the common carotid artery (Distens). RWTd, A/E, and IMT in SI (RWTd, 0.41+/-0.07; A/E, 1.21+/-0.41; IMT, 0.69+/-0.17 mm) and SII-III patients (0.40+/-0.08, 1.38+/-0.33, 0.80+/-0.21 mm) were larger than those in NOR patients (0.33+/-0.03, 0.86+/-0.21, 0.56+/-0.10 mm) (p < .01). Furthermore, LVMI in SII-III (135.5+/-35.5 g/m2) patients was larger than that in NOR patients (99.4+/-17.5 g/m2) (p < .05). RWTd in HN patients (0.37+/-0.06) was significantly higher than that in NOR patients (p < .05). A/E tended to be larger in HN than in NOR patients (p < 0.1). In the normotensives, no significant difference in any of the parameters was detected between those with optimal (n = 19) and normal (n = 19) blood pressure. Thus, both morphological and functional changes were associated with elevation of blood pressure. Cardiac morphological adaptation and functional impairment were present even in subjects with high-normal blood pressure level, while there were no significant differences between the normal and optimal subsets.