Ethical issues facing psychologists working in police settings involve representations of the effectiveness of psychological programs, representations of the psychologist's competency, confidentiality, responsibility to client organizations, and design of research and utilization of its findings. For example, psychologists may be asked to provide services which they find of doubtful effectiveness. Furthermore, a psychologist may be asked to assist in a program of police personnel selection which involves a different level of psychometric theory than many clinicians are accustomed to practicing and familiarity with such issues as equal opportunity guidelines. Lack of competence in these areas can have serious financial, legal, and social consequences. Many of these issues can be resolved through adequate forethought, and planning of the psychologist's contract with the law enforcement agency, and periodic reviews of the psychologist's work relationship. The psychologist should also be committed to empirical resolution of disagreements over matters of fact. For example, in representing psychological programs, the psychologist should consider the adequacy of the design of evaluative studies and should apply to proposed programs evaluative requirements looked for by funding sources, while honoring the client agency's own standards for evaluation. The psychologist should also point out the limitations of psychological knowledge and generalizations. Questions of public policy and future roles of psychologists in the law enforcement system are discussed. Notes and about 50 references are included.