ABSTRACT Cardiovascular disease (CVD) has become a leading cause of morbidity and mortality in persons with HIV (PWH). Although clinical guidelines recommend detecting and addressing CVD risk among PWH, CVD prevention has not been effectively implemented in routine HIV Care. Addressing this implementation gap is critical for reducing the disproportionately greater burden of adverse CVD outcomes facing PWH. My K01 research aimed to address this gap by examining CVD risk among PWH, CVD preventive practices in HIV care, and implementation strategies to improve these practices. My work showed CVD risk in PWH is driven by traditional risk factors (e.g., hypertension) which HIV clinical guidelines recommend addressing. My K01 research also showed that lack of awareness about clinical guidelines, low clinician motivation to follow the guidelines, lack of CVD preventive resources, and the clinic culture influence guideline adoption. I then developed an agent-based model to simulate the effects of implementation strategies on these barriers: I found education, audit and feedback, and leadership engagement are promising strategies to improve guideline adoption. To determine if these findings are valid and aligned with current HIV care practices, my model needs to be externally validated using data from diverse HIV care contexts. Further, to determine its acceptability and real-world relevance, the model needs to be evaluated by HIV stakeholders and refined through participatory modeling approaches. Thus, the overall goal of this R03 application is to externally validate and refine my K01 model through participatory agent-based modeling. First, I will externally validate the model that simulates the effects of implementation strategies on hypertension care guideline adoption (AIM 1). Second, I will evaluate and refine the model through participatory agent-based modeling with HIV stakeholders (AIM 2). The proposed study responds to NHLBI’s call to explore CVD prevention in the HIV population and to optimize implementation research to improve health. This study will contribute a tool that HIV decision makers can use to inform their CVD prevention efforts, and a prototype implementation strategy that can be tested in real-world HIV clinics.