OBJECTIVES Electrocardiographically assessed left-ventricular hypertrophy (ECG-LVH) is a particularly high-risk phenomenon that is a part of every hypertensive patient’s initial work-up. Several cross-sectional studies have demonstrated that home blood pressure (BP) has a stronger relation to LVH than office BP. However, longitudinal evidence on the association between home BP and target organ damage is scarce to nonexistent. METHODS We studied in a sample of 615 community-dwelling participants (mean age at baseline 53.7 ± 7.2, 58% women) whether change in home BP is more strongly associated with change in ECG-LVH than change in office BP over an 11-year follow-up. RESULTS Pearson’s correlation coefficients between changes in home/office SBP and changes in Sokolow-Lyon index, Cornell voltage, Cornell product and R wave amplitude in aVL were 0.21/0.18, 0.28/0.17, 0.25/0.16, and 0.32/0.20, respectively (asterisk indicates P textless 0.05 for between-method difference in correlations with Steiger’s z test). For change in home/office DBP and change in the aforementioned ECG-LVH indexes, the correlations were 0.12/0.12, 0.20/0.15, 0.16/0.12, and 0.28/0.19. Multivariable-adjusted regression modelling provided similar results. No clinically significant increase in correlations between home BP and ECG-LVH indexes occurred after the fourth day of home BP measurement. CONCLUSION Our study demonstrates for the first time the superiority of home BP over office BP in the follow-up of left ventricular mass. The results of this and previous studies underline the importance of using out-of-office BP measurements as the primary method for assessing blood pressure levels.