A paradigm shift in public health and medicine has broadened the field from a singular focus on the ill effects of negative states and psychopathology to an expanded view that examines protective psychological assets that may promote improved physical health and longevity. We summarize recent evidence of the link between psychological well-being (including positive affect, optimism, life meaning and purpose, and life satisfaction) and physical health, with particular attention to outcomes of mortality and chronic disease incidence and progression. Within this evolving discipline there remain controversies and lessons to be learned. We discuss measurement-related challenges, concerns about the quality of the evidence, and other shortcomings in the field, along with a brief discussion of hypothesized biobehavioral mechanisms involved. Finally, we suggest next steps to move the field forward.