Left ventricular (LV) hypertrophy is diagnosed on the basis of LV mass measurement at echocardiography. However, various thresholds for defining LV hypertrophy have been published, ranging from 111 to 134 g/m2 and from 100 to 125 g/m2 in men and women, respectively. The aim of our study was to evaluate variations in the prevalence of LV hypertrophy induced by the application of different threshold values among hypertensive subjects. LV mass was calculated in 349 hypertensive patients from an M-mode LV tracing obtained by left parasternal view in 83% and by subcostal view in 17% of patients. The prevalence of LV hypertrophy ranged from 17% to 39%, according to the threshold value applied (from 10% to 47%, and from 19% to 39% in women and men, respectively). As expected, the prevalence of LV hypertrophy in obese patients of both sexes was higher when applying the usual height-indexed threshold (143 and 102 g/m for men and women, respectively) than when applying the usual body surface area-indexed threshold (134 and 110 g/m2 for men and women, respectively). The use of normalized thresholds when comparing different indexation methods (in this case, 145 g/m for men, 120 g/m for women) will minimize these variations in part due to the threshold choice. Considering the clinical and therapeutic implications associated with the presence of LV hypertrophy, better standardization of definitions is needed; this could be based either on better-designed cooperative normality studies or meta-analysis of risk stratification.