A positive family history of hypertension (+FHH) is associated with non-exercise induced increases in left ventricular mass (LVM) and high-normal blood pressure (BP). Regular physical activity (PA) can lead to non-pathological increases in LVM, but evidence shows adults with elevated BP can decrease LVM with PA. PURPOSE: To determine if a +FHH is associated with a greater LVM indexed to body surface area (BSA) compared to a negative family history of hypertension (-FHH) group within a sample of young, mostly active healthy adults. METHODS: Healthy young (18-32yrs) participants self-reported family history of hypertension (FHH) status and habitual moderate and vigorous PA frequency as days per week with at least 10 minutes of recreational activity. Participants then underwent an echocardiogram. Participants were excluded from this retrospective analysis if there was a prior diagnosis of cardiovascular-related disease or hypertension. Within-group normality of each variable was tested using the Shapiro-Wilk test. Simple bivariate comparisons between groups were made using unpaired t-tests for normally distributed variables and Mann-Whitney tests when normality was violated. LVM/BSA was logarithmically transformed prior to ANCOVA testing due to non-normality. RESULTS: Of the 61 participants, 32 (M=11, W=21; non-active=8) reported -FHH and the remaining 29 (M=13, W=16; non-active=2) reported a +FHH. While still in the normal range, the +FHH group displayed greater systolic BP (-FHH 112±12, +FHH 117±12 mmHg, p=0.043), but similar values for all other demographic information when compared to the -FHH group (age -FHH 23±3, +FHH 23±2 yrs, p=0.116; BSA -FHH 1.74±0.20, +FHH 1.74±0.21 m2 , p=0.903; diastolic BP -FHH 68±6, +FHH 69±8 mmHg, p=0.287; resting heart rate -FHH 66±13, +FHH 64±9 bpm, p=0.578; moderate exercise frequency -FHH 1.8±1.8, +FHH 2.6±2.1 days/week, p=0.117; vigorous exercise frequency -FHH 2.5±2.2, +FHH 3.4±2.0 days/week, p=0.105). The +FHH group had greater LVM (-FHH 129.5±41.8, +FHH 155.2±42.6 g, p=0.015) and LVM/BSA (-FHH 73.5±17.4, +FHH 88.4±17.3 g/m2 , p=0.004). Separate ANCOVA models accounting for moderate and vigorous PA found that FHH status independently predicted LVM/BSA and PA frequencies were a significant modifier (ANCOVA controlling moderate PA: FHH status p=0.004, partial η2 =0.133; moderate PA p=0.020, partial η2 =0.089), (ANCOVA controlling vigorous PA: FHH status p=0.004, partial η2 =0.132; vigorous PA p=0.007, partial η2 =0.117). CONCLUSION: This preliminary analysis suggests that young adults with a family history of hypertension have elevated left ventricular mass compared to their counterparts without a family history of hypertension. This finding is independent of their habitual moderate and vigorous physical activity patterns.