Ambulatory blood pressure monitoring (ABPM) is the most reliable and precise measurement in diagnosing hypertension. We hypothesized that masked uncontrolled hypertension (MUCH) may be more prevalent in individuals with electrocardiographically left ventricular hypertrophy and normaloffice blood pressure (BP). To prove the hypothesis, we investigated the association between electrocardiographically left ventricular hypertrophy (LVH) and MUCH detected by ABPM in individuals with normal office BP.  We conducted retrospective study for 77 subjects who received electrocardiography (EKG) and ABPM from 2018 to 2019 year in Veterans Healthcare Service Medical Center. Electrocardiographic LVH was defined as the length of S wave in V1 (SV1) + the length of R wave in V5-6 (RV5-6)≥35 mm. MUCH was determined by 24 hour mean BP≥130/80 mmHgin ABPM and normal office BP (<140/90 mmHg). Subjects were divided into 2 groups of non-LVH group and LVH group. Independent T-test and Chi-square test were conducted to compare the clinical characteristics of subjects between two groups. Correlation analysis was performed to identify the relationship between EKG and ABPM. Logistic regression analysis was used to evaluatethe association MUCH and other factors. The number of subjects in non-LVH group and LVH group was 42 (54.5%) and 35(45.5%), respectively.LVH group manifested the lower prevalence of DM, lower BMI and higher creatinine level. Proportions of MUCH and nocturnal hypertension were higher in LVH group than non-LVH group (Table 1). In correlation analysis, night-time systolic BP showed the positive correlation with SV1+ RV5-6 (r=0.282, p value=0.014) and RV5-6(r=0.320, p value=0.005), and night-time diastolic BPwas positively correlated with SV1+RV5-6(r=0.293, p value=0.010), RV5-6(r=0.268, p value=0.019). Logistic regression analysis indicated that LVH was significantly associated with MUCH (3.3 [1.2-9.3]) (Table 2). Electrocardiographically detected LVH was significantly associated with MUCH.These findings suggest that ABPM may be potentially useful in detecting MUCH among individuals with normal office BP and electrocardiographic LVH.