This chapter draws on feminist materialist scholarship in bioethics to discuss the parallels between what is known as the brain disease model of addiction and the emerging notion of chronic pain as a brain disease. The authors describe the development of biological models of addiction and chronic pain, and offer an ethical analysis of the scientific, institutional and rhetorical forces that have contributed to framing addictions and chronic pain through the brain disease model. Drawing on scholarship in feminist science and technology studies, the chapter explores how concepts of identity and agency are intertwined with presumptions about technology, progress, objectivity and evidence.