The Global Assessment of Functioning (GAF) is a numeric scale (from 0 to 100) used by doctors and mental health clinicians to rate the social, occupational and psychological functioning of adults.

The scale is found in the Diagnostic and Statistical Manual of Disorders (DSM-IV), which is published by the American Psychiatric Association, and provides the diagnostic criteria for mental disorders.

A GAF score is a useful piece of evidence for a Social Security disability claim. The GAF score is often included in mental health progress notes or evaluations, and it provides an excellent snapshot of the patient's functioning.