AIM: Findings regarding the association of left ventricular mass (LVM) and new-onset hypertension are based on blood pressure measured in the office. We sought to assess the value of LVM in predicting in-office and out-of-office incident hypertension in members of the general population enrolled in the Pressioni Monitorate E Loro Associazioni study. METHODS: The study included participants with normal office (n = 792), home (n = 714) and 24-h (n = 825) ambulatory blood pressure (ABP) at baseline evaluation who had a readable echocardiogram at entry and at the end of follow-up. Each normotensive group was divided into quartiles of LVM indexed (LVMI) to height. RESULTS: Over a follow-up of 148 months cumulative incidence of new office, home and 24-h ABP hypertension were 35.9, 30.7 and 36.1%, respectively. In fully adjusted models (including age, sex, BMI change during follow-up, baseline serum glucose, creatinine, total cholesterol office, home and 24-h SBP and DBP). higher LVMI values (i.e. the highest vs. the lowest quartile) were independently associated with an increased risk of home [odds ratio (OR) = 2.14, 95% confidence interval (CI) 1.21-3.77, P = 0.008] and 24-h ABP hypertension (OR = 1.70, 95% CI 1.05-2.76, P = 0.03). This was not the case for new-onset office hypertension (OR = 1.61, 95% CI 0.94-2.74, P = 0.07). CONCLUSION: Our study provides the first evidence that in normotensive individuals the magnitude of LVMI is independently associated with the risk of incident out-of-office hypertension.