The current study examined the susceptibility of the Adaptive Behavior Assessment System-2nd edition (ABAS-II; Harrison & Oakland, 2003) and the Scales of Independent Behavior-Revised (S1B-R; Bruininks, Woodcock, Weatherman, & Hill, 1996) to the feigning of adaptive functioning deficits. Using four different instruction sets, the authors evaluated whether the provision of diagnostic information (a form of coaching) improved participants' ability to simulate adaptive deficits commensurate with a diagnosis of mental retardation. The authors found that the ABAS-II was quite vulnerable to believable manipulation by raters, while the SIB-R was not. In fact, exaggeration on the SIB-R was easily detected regardless of the information provided. Implications regarding the use of these measures in Atkins mental retardation evaluations are discussed.