The diagnostic and statistical manual of mental disorders (DSM) is an evolving document that serves the many mental health care disciplines as the primary reference guide for classifying mental disorders. While the successive framers of the DSM have attempted to base it on scientific evidence, political and economic factors have also shaped the conceptualization of mental illness. These economic and institutional forces have reinforced the DSM's use of a medical model in understanding psychopathology. Though the scientific evidence for a medical model is mixed and evidence for other types of conceptualizations have been given less attention, the medical model provides for reliable diagnoses that allot diverse benefits to treatment providers and researchers, as well as to the pharmaceutical and healthcare industries. This article will outline the development of a medical model of mental illness, highlighting connections between this model and corporate and political interests, and will show how this model relates to the various revisions of, and developments within, the DSM. Such an analysis is especially relevant today as the field looks towards the publication of the newest revision of the DSM and attempts to understand and integrate its proposed changes into current treatment, theory, and research.