Project Summary/Abstract Career Goal. My long-term career goals are: (1) to obtain and secure a full-time tenure track appointment; and (2) to become an independently funded community-engaged Latinx public health scientist to address immigrant health as well as substance use/HIV risk in Latinx populations. This research and training grant will provide me with the opportunity to fortify my research skills as a postdoctoral fellow at FIU to successfully transition to a prevention intervention scientist that addresses prominent health inequalities faced by stimulant-using LMSM. Career Development. This K99/R00 research and training plan will catalyze my efforts to acquire the advanced training necessary to develop and test culturally informed behavioral interventions addressing the intersection of stimulant use and HIV risk in LMSM. During the K99 phase, my training goals consist of (1) developing advanced competencies in designing culturally informed evidence-based interventions;(2) pursuing advanced training in Randomize Control Trial methods necessary to examine the feasibility, acceptability, and preliminary efficacy of a culturally informed behavioral intervention and (3) acquire knowledge in the application of SNA methods to assess the effects of a culturally informed behavioral intervention on participant's social network composition. Research Project. Latinx communities are the fastest-growing group in the US.24 LMSM (foreign and US-born) are disproportionately affected by HIV and other sexually transmitted diseases. The K99/R00 proposal will focus on this underserved population of stimulant-using LMSM who are in desperate need of culturally informed interventions to mitigate co-occurring stimulant use and HIV risk in the era of PrEP. Developing a behavioral intervention that addresses cultural factors and social networks as key determinants of stimulant use and HIV risk in LMSM represents a viable strategy to reduce stimulant use, decrease engagement in condomless anal sex (CAS), and support PrEP uptake in LMSM. Specific Aims. (1) Conduct formative research through mixed methods to develop a culturally informed intervention targeting co-occurring stimulant use and HIV risk in LMSM who are not on PrEP and (2) Conduct a pilot Randomize Control Trial to test the feasibility, acceptability and preliminary efficacy of a culturally informed intervention for optimizing PrEP uptake as the primary outcome with 60 stimulant-using LMSM. Mentorship Team: My efforts will be guided by an accomplished, interdisciplinary team of mentors committed to support my transition to an independent investigator.