There might be limitations in identifying concentric left ventricular (LV) geometry by ratio of diastolic posterior wall thickness (WT(p)) to cavity radius, defined as relative wall thickness (RWT(p)). This study has been designed to evaluate age effects on RWT(p). WT(p), mean of septal thickness and WT(p) (WT(m)), and cavity radius were cross-sectionally evaluated in 766 1- to 85-year-old, normotensive, nonobese subjects and 331 hypertensive Italians (used as a test series). RWT(p) > or =0.43 defined "traditional" concentric LV geometry. The ratios WT(m)/radius (RWT(m)) and RWT(p) increased by 0.005 and 0.006 per year of age in the age stratum up to 17 years and by 0.002 in the older age stratum (18 years or older; all P<0.0001). Thus, RWT(m) and RWT(p) were normalized to average age in both age strata (10 and 46 years) by age-specific regression coefficients. The 90th and 95th percentiles of age-normalized RWT(p) or RWT(m) were 0.40 and 0.42 or 0.41 and 0.43, respectively, in adults and 0.36 and 0.39 or 0.36 and 0.38, respectively in young subjects. In hypertensive subjects, traditional RWT(p) cutoff identified 74 subjects (22%) with concentric LV geometry; by 95th or 90th normal percentiles, normalized RWT(m) identified 112 (34%), or 149 (45%) subjects with concentric LV geometry, and normalized RWT(p) 29% and 39%, respectively (all P<0.0001 versus unadjusted RWT(p)). Thus, prevalence of concentric LV geometry increases with age-normalized RWT. Accordingly, we suggest that concentric LV hypertrophy be defined by coexistence of high LV mass with age-normalized RWT(m) >0.41 or RWT(p) >0.40. Further studies are required to establish prognostic implications of our findings.