Adulterants and urine substitutes that are designed to defeat drug tests are readily available and can be easily researched or purchased over the Internet. Utilizing Google, PsychInfo, and Medline, we searched the Internet and psychiatric and medical literature to identify a comprehensive list of products, compounds, and methods of urine tampering, as well as data on their efficacy. These products, compounds, and methods are described, and literature on their effectiveness in masking drug use is reviewed. Additionally, we identify and review methods for detecting tampering of urine screens and tests. It is recommended that clinicians and researchers involved in urine drug screening and testing consider the possibility of tampering when designing treatment programs and research protocols and employ methods to detect its occurrence when appropriate.