Assessment, particularly testing, permeates every facet of people's lives. Almost every subset of psychologists uses tests. Researchers use tests to acquire data from those who participate in their studies. Clinical psychologists administer tests for diagnostic purposes and to monitor the course of psychotherapy. School psychologists assess children to determine their eligibility for possible placement in special education programs. Counseling psychologists use vocational, occupational, and interest tests to guide career development and measure problemsolving skills throughout the life span. Forensic psychologists use tests to help courts determine the best placement for children whose parents are divorcing or to assess whether a criminal defendant is competent to stand trial or should be held responsible for an otherwise criminal act. Industrial and organizational psychologists measure skills and job knowledge of those seeking employment or promotion. And, of course, academics often devise their own instruments to assess what their undergraduate and graduate students have learned.As the nonexhaustive list above illustrates, assessment can take many forms. Each form may have its own ethical implications. For example, when clinicians use intelligence scales, paper-and-pencil personality tests, or projective techniques, issues of privacy and informed consent arise. When psychologists in employment settings use tests, issues of dual loyalties arise: For whom is the psychologist working and to whom does the psychologist owe the primary obligation of fidelity-the test taker or the employer? When school psychologists assess children for special education placement, who is the client-the child, the parent, or the school system that is paying the evaluator? When a researcher gathers data through tests, questions of informed consent and deception become important (see chap. 8, this volume). When forensic clinicians evaluate a criminal defendant, are they working on behalf of the prosecution, the defense, or the court (see chap. 9)? And regardless of the assessor's role, the issue of competence becomes pervasive. Are the tests that are used psychometrically sound, and are the interpretations and judgments that psychologists make from the data valid? Finally, the advent of computerized testing in general and the increased use of so-called honesty or integrity tests in employment in particular open such discussions to a whole new set of issues.This chapter can only provide an introduction to the complex ethical issues inherent to gathering, storing, interpreting, and disseminating information about test takers that is gleaned from assessment. Such technical issues as validity, reliability, norming, and standardization are addressed here only if they are relevant to ethical and social issues. To gain a broader perspective on both technical and social policy questions, see the two special issues 249