Workplace drug testing is conducted to ensure safety and promote productivity while deterring the use of drugs by an employee. There are several reasons for testing, which include pre-employment, random, post-accident, reasonable suspicion, return to duty, and follow-up testing. Drug addiction is a disease that interferes with individuals’ social and work lives. Those struggling with addiction may turn to extreme measures to avoid workplace drug testing or subvert the testing process. As a result, individuals may use household chemicals or other substances purchased on the Internet to adulterate urine specimens in an attempt to “beat” a drug test. Some of these agents can affect either the initial or confirmation testing methods. In this chapter, the percentage of adulterated urine specimens submitted for workplace drug testing is addressed. Fortunately, tests to identify adulterated specimens are available prior to analysis of these specimens.