Midlife (45-64 yr) Mexican-American (MA) men are susceptible to future burden from cardio-metabolic diseases because of numerous factors, most notably less healthful dietary and physical activity (PA) behaviors coupled with low participation in chronic disease prevention and management efforts. Thus, there is an urgent need to understand how to promote health-enhancing diet and PA behaviors in this understudied group of the population. The objective of this application is to use a mixed-methods approach to inform the development of and pilot test a gendered- and culturally-tailored diet- and PA intervention for cardio-metabolic disease prevention among midlife MA men. This objective will be attained by addressing the following specific aims: (1) conduct qualitative research with midlife MA men and their significant others (e.g. spouse, partner, close family member), and key informants (stakeholders from the MA community) to identify: (a) knowledge, perceptions, and behaviors regarding what constitutes healthful diet and PA practices; (b) perceived barriers and enablers of dietary and PA behavior change, (c) proposed strategies to promote dietary and PA behavior change, (d) perceived resources and assets for implementing dietary and PA behavior change interventions, and (e) masculine, cultural, and social identities that interact to influence interest and engagement in healthy lifestyle behaviors; and (2) assess the initial efficacy, feasibility and acceptability of a gender-tailored and culturally-relevant diet and PA behavior change pilot intervention targeting midlife MA men. Phase I of the project will entail focus groups to identify determinants of midlife MA men’s health behaviors, existing good practices and health- promoting values and behaviors, and acceptable intervention strategies. The proposed project will use intersectionality, which examines how the blending of identities and experiences create more accurate reflection of the determinants of men’s health behaviors, within the context of the sociocultural determinants of health, as the conceptual framework. A “grassroots” approach will also explore beliefs, barriers and enablers to dietary and PA change identified by significant others and community stakeholders Information collected during Phase I will inform the development of intervention materials and processes that will be pilot-tested during Phase II. Phase II will consist of a randomized controlled trial to test the initial efficacy, feasibility and acceptability of a gender-tailored, culturally relevant dietary and PA intervention targeting midlife MA men. Innovation lies in our study being the first to apply an intersectional approach in health disparities research with midlife MA men, a severely understudied and high-risk subgroup. To date, no interventions have been developed or adequately tailored to address issues unique to MA men 45-64 yr. Thus, the proposed research is significant be- cause it addresses a critical gap and will inform the development of lifestyle-based interventions targeting mid- life MA men. The proposed project will also establish the foundation for a subsequent test of intervention efficacy, as well as future translation and dissemination in varied community settings.