Over the past two decades, HIV epidemiology among Black sexual minority men (SMM) has raised crucial questions about the role of age and generational effects on health risks for this group. U.S. data showed that although HIV incidence was highest among those ages 13–24 in 2010, by 2018, the most affected group shifted to men ages 25–34, with a significant 42% increase in HIV+ diagnoses in that cohort. CDC data from 2022 showed that 25–34-year-olds continued to experience greater incidence overall while incidence among younger cohorts has decreased. This age-related trend raises the question of whether young adulthood represents a consistent period of heightened HIV vulnerability (an age effect) or whether those who were at greatest risk as adolescents continue to experience systemic barriers and sustained risk as they age (a cohort effect). Projections from modeling studies reinforced the urgency of this issue, estimating that 50% of U.S. Black SMM would acquire HIV by age 30. Therefore, this chapter introduces Life Course as a key theoretical framework to examine health vulnerability among Black SMM more carefully, emphasizing how historical time, social context, and individual agency collectively determine health trajectories. The chapter also considers how generational differences in exposure to public health messaging, medical advancements, and evolving social norms influence risk perceptions, prevention engagement, and healthcare utilization broadly. Key Life Course constructs including lives over time (trajectories), historical time and place, timing of life transitions, linked lives, and human agency, are discussed to contextualize how social determinants of health operate over time to affect the lives of Black SMM. HIV epidemiology is used as a backdrop example to demonstrate why a Life Course perspective is essential to study health more holistically for Black SMM everywhere.