AbstractThe heated debate over the reliability and effectiveness of IQ testing has spilled over into the realm of mental retardation. Indeed, the recent Federal Appeal Court (9th Circuit) decision to uphold the Larry P. v. Riles decision has elevated the MR IQ testing stigma controversy from a regional issue (California) to a national concern. Clearly, the MR dimension adds new relevance to the IQ controversy, notably: What do IQ tests really measure and for what purpose and which populations? This paper examines the role of IQ testing within the larger MR evaluation process, looking at this phenomenon from both the historical and contemporary perspectives.