Police officers are a part of society and will reflect society's norms and values. In the case of drug use by police officers, it is a serious concern because it can impair an officer's ability to function appropriately and effectively; it increases the risk of officer corruption; and it undermines the public's confidence in the police and their integrity. One of the most controversial components of a police agency's efforts to prevent and counter officer drug use is the implementation of a bioassay-based drug-testing program. This chapter describes how such programs operate, as well as the technical drug assays that are available to police agencies. It also reviews the questions, problems, and issues related to interpreting and responding to a positive drug assay. This review places police drug-testing programs and policies in the context of general workplace testing and identifies those elements that it shares with the programs, along with the unique issues that police agencies face. This chapter presents data on the outcome of an applicant-screening process by using both a traditional technology (urinalysis) and a recent technology (hair analysis). A review of these data indicates that although the majority of applicants can pass a drug test, there is a significant group of people seeking work in policing who have used drugs. Police agencies may want to consider using multiple drug-testing modalities to maximize the identification of various drugs whose characteristics can be an important consideration in interpreting drug-test results. 1 figure, 12 tables, and 57 references