Biological drug testing is a tool that provides information about an individual's recent substance use. Like any tool, its value depends on using it correctly; that is, on selecting the right test for the right person at the right time. This document is intended to clarify appropriate clinical use of drug testing in addiction medicine and aid providers in their decisions about drug testing for the identification, diagnosis, treatment, and recovery of patients with, or at risk for, addiction. The RAND Corporation (RAND)/University of California, Los Angeles (UCLA) Appropriateness Method (RAM) process for combining scientific evidence with the collective judgment of experts was used to identify appropriate clinical practices and highlight areas where research is needed. Although consensus panels and expert groups have offered guidance on the use of drug testing for patients with addiction, very few addressed considerations for patients across settings and in different levels of care. This document will focus primarily on patients in addiction treatment and recovery, where drug testing is used to assess patients for a substance use disorder, monitor the effectiveness of a treatment plan, and support recovery. Inasmuch as the scope includes the recognition of addiction, which often occurs in general healthcare settings, selected special populations at risk for addiction visiting these settings are briefly included.