In this chapter, we review how the term “selection effects” has been used by researchers, what processes are implied by the term, and how analyses of selection effects can contribute to our understanding of the associations between socially structured experience and individual health and well-being. Our review draws on the life course perspective to suggest that selection effects represent more complex processes than are often recognized and to create a template for more nuanced analyses of those processes. Through logical arguments and examples, we build the case for a sociological research agenda on selection processes equivalent in importance and relevance to our long tradition of research on social causation.