Among concerns inherent in psychological testing is the possibility that examinees might perform less than accurately or honestly when responding to test items (Lezak, 1983). In context of some legal proceedings, individuals may stand to gain by performing poorly on physiological tests (Anastasti, 1988). For example, defendants could attempt to falsify their answers to impersonate an individual with mental retardation for the purpose of raising issues of incompetence to stand trial, nonresponsibility, or mitigation. In some states, a finding of mental retardation may mean the difference between a life sentence and execution for a defendant convicted of a capital crime. The validity and reliability of intelligence testing instruments are of vital importance in determining the existence of mental retardation. The purpose of this study was to examine the possibility that subjects could deliberately and successfully falsify responses on corresponding subtests of two major intelligence tests, the Wechsler Adult Intelligence Scalre-Revised (WAIS-R) (Whechsler, 1981) and the Stanford-Binet Intelligence Scale-Fourth Edition (SB:FE) (Thorndike, Hagen, and Sattler, 1986a) to simulate the existence of mental retardation. Subjects were administered and Comprehension subtests from both the WAIS-R and the SB:FE and instructed to perform less accurately and less honestly than their capabilities naturally provide. A control procedure was also administered. Corresponding standardized scores (Normal Curve Equivalency [NCE]) were compared for significant differences using a one-factor, repeated measure ANOVA. Latency periods recorded and analyzed using descriptive statistics an an ANOVA, and qualitative data obtained in debriefing sessions were also reported. Statistical analyses indicated that subjects were unable to score similarly on both tests when simulating mental retardation (