Background Regression of left ventricular ( LV ) hypertrophy ( LVH ) has been a goal in clinical trials. This study tests the external validity of results of clinical trials on LVH regression using a large registry from a tertiary care center, to identify phenotypes less likely to achieve regression of LVH . Methods and Results Patients from the Campania Salute Network, free of prevalent cardiovascular disease, but with echocardiographic LVH (defined as LV mass index [LVMi] >47 g/m ^2.7 in women and >50 g/m ^2.7 in men) were included. During a median follow‐up of 67 months, clear‐cut regression of LVH was documented in 14% of patients (13±8% reduction of initial LVMi ) or 23% when also considering those with a reduction of LVMi ≥5 g/m ^2.7 . Patients with persistent LVH were older with longer duration of hypertension, suboptimal blood pressure (BP) control, larger body mass index, LV mass, and carotid intima‐media thickness and included more women and subjects with diabetes mellitus, isolated systolic hypertension, and metabolic syndrome (all P <0.05). Number and class of antihypertensive drugs during follow‐up did not differ between groups. In multiple logistic regression analysis, older age, female sex, obesity, higher baseline LVMi and carotid intima‐media thickness, and suboptimal BP control were significant covariates of persistent LVH (all P ≤0.01), independent of diabetes, duration of hypertension, isolated systolic hypertension, follow‐up time and number and class of antihypertensive drugs. Conclusions Early initiation of antihypertensive treatment, aggressive BP control, and attention to metabolic aspects are critical to avoid irreversible LVH .