Abstract Body (Do not enter title and authors here): Intro: Young adults with perinatally acquired HIV (YPHIV) have higher morbidity and mortality than uninfected persons. Antiretroviral therapy (ART) has extended life expectancy making adult CV disease a concern. Perinatal exposure to HIV increases inflammation which is associated with increased arterial stiffness which predicts CV disease. Aims: We compared arterial stiffness between YPHIV and young adults perinatally HIV exposed but uninfected (YPHEU), and evaluated the association of type and duration of ART regimens, HIV disease severity, and cardiac structure and function with arterial stiffness. Methods: In a substudy of the Pediatric HIV/AIDS Cohort Study, 150 participants (95 YPHIV, 55 YPHEU, mean 23.4 yrs, 60% female, 72% Black, 24% Hispanic) had echocardiography and pulse wave velocity (PWV) measured. We compared PWV between YPHIV and YPHEU, adjusting for covariates. Among YPHIV, we fit linear regression models to evaluate the association of current (within 1 year of PWV) and historical measures of HIV disease severity with PWV. We computed correlations between PWV and measures of left ventricular (LV) structure and function, overall and by HIV status. Results: Mean PWV and hemodynamic parameters did not differ between YPHIV and YPHEU (YPHIV 5.63 vs YPHEU 5.39 m/s; p=0.5). HIV control was good (82% with viral load <400 copies/ml), 91% used combination ART: integrase strand inhibitors (INSTIs; median duration 4.6 years), protease inhibitors (PIs 15.1 years), or non-nucleoside reverse transcriptase inhibitors (NNRTIs 5.2 years). Most participants had normal PWV compared to healthy controls but all values above 11.8 m/sec (Figure, level associated with CV events in adults) were only in YPHIV. Only weak correlations were observed between PWV and echocardiographic measures (<0.20) in both YPHEU and YPHIV. Among YPHIV, HIV severity measures were not associated with PWV using either current or historical measures. Mean PWV was 1.68 (-0.36, 3.72) m/s higher among YPHIV with current PI use than those on INSTIs, and 1.58 (-0.94, 4.11) m/s higher than those on NNRTIs, although these differences were not significant. Conclusions: PWV was within normal ranges in most YPHIV and YPHEU although 5% YPHIV had elevated PWV. PWV may be higher with PI use due to cardiometabolic side effects. Successful HIV treatment and control of traditional CV risk factors may prevent premature vascular aging and subsequent cardiac compromise in YPHIV.