While specimen collection and preparation are often beyond the control of the laboratory, other steps in the testing process are not. The laboratory staff is responsible for test methods, quality assurance methods, medico-legal documentation, and result reporting and interpretation. All steps in the drug testing process are discussed in detail, with special emphasis on the laboratory's role in taking the necessary precautions to ensure the viability of test results. To ensure accuracy and reliability of drug test results, the laboratory must monitor the entire testing system, from specimen pick-up to reporting of results. When choosing a laboratory to carry out drug tests, client companies must evaluate their own needs and look for a laboratory that promises and delivers accuracy, service, quick turnaround time, and a wide range of testing methods. 21 references.