A positive drug test in the workplace cannot determine what the pattern of an individual's drug use is or whether drug-induced work impairment exists. A clinical and performance evaluation is needed to answer these questions. The main reasons for workplace drug abuse include performance facilitation, relief of boredom, drug addiction, and self-medication of side effects of other drugs. Although most companies require yearly physical examinations of their employees, some physicians miss the opportunity for early diagnosis of alcohol or other drug dependence due to uncertainty about their role, stereotypical views of drug abusers, concern about the person's anger if questioned, or lack of knowledge. Supervisors and safety personnel can also identify possible drug abusers by observing physical and behavioral signs. Participation in a peer group provides a sensitive method for detecting impending or actual relapse to drug use. Additional workplace issues include the role of the medical review officer, the use of specific urine testing instruments and procedures, referral and treatment, confidentiality, safety, and legal issues. Tables and 32 references