This article reviews the results of two decades of research comparing the self-reports of hundreds of juvenile and adult sex offenders with reports made after several months of treatment, with the benefit of conditional immunity for undisclosed sexual crimes, and subject to polygraph verification. Study findings indicated that adults would lie and understate the number of sexual crimes they had committed by a factor of five to six, adults would lie and underreport their history as a juvenile sex offender, adults would lie and overreport their history of childhood sexual victimization, and with polygraphs, they reported six times as many victims with confessions that they were sexually offending as juveniles. The polygraph is viewed as a significant tool for both assessment and management. However, since polygraph examinations introduce complex legal questions, they should be approached with extreme care. Tables