Because most health insurance companies, health maintenance organizations (HMOs), and clinics require a diagnosis based on DSM (Diagnostic and Statistical Manual of Mental Disorders) criteria, it is essential that mental health professionals are competent in making accurate and appropriate DSM diagnoses. The current version, DSM-IV-TR (American Psychiatric Association, 2000), has been designed for use across a variety of treatment settings, including inpatient, consultation-liaison, clinic, private practice, and primary care, and is the standard classification of mental disorders used by mental health professionals in the United States. For the purpose of making a DSM diagnosis, therapists-in-training should be familiar with the DSM’s diagnostic classification, diagnostic codes, diagnostic criteria sets, and a strategy for making a five-axes diagnosis. This chapter describes these DSM factors and the process of making a DSM diagnosis, and it illustrates this process with case examples.