The polygraph test and procedures used by polygraph examiners are described and compared to other methods of detecting deception. Controversy regarding the validity and reliability of polygraph results is reviewed in the context of laboratory and field research. Pros and cons of the procedure's use are discussed, and factors contributing to the accuracy of results are considered. The basic principles upon which psychometric tests are founded are reviewed, and it is shown that the polygraph falls short of psychometric standards. Difficulties with definitions of truth and honesty are considered, and it is noted that polygraph results are unlikely to provide a good indication of how an individual will behave in different situations. Theories of emotion are reviewed, with emphasis on the reciprocal nature of emotional expression and its implications for polygraph testing. Also described are the procedures used in security vetting, employment screening, and interrogation. Finally, legal and civil rights issues surrounding the use of polygraph testing in Great Britain and the United States are addressed. Student guide, index, glossary, annotated bibliography, and approximately 240 references.