The adequacy of neuropsychological norms is dependent on the characteristics of the subjects whose data are used. Volunteer participants and neurologically normal participants in major normative studies show markedly different patterns of test performance that reflects on the inadequacy of using volunteer participants to develop norms. In this study when all of the Halstead Reitan Battery norming studies with an N of 200 or more were examined, Wechsler FSIQ score differences of approximately 1 standard deviation above average for the volunteer normative participants was found. The norms from the norming study using neurologically normal patients were essentially average. The exclusion of neurologically suspect participants from volunteer normative studies lead to a bias reflected in artificially inflated levels of performance, and a restricted range of variation. This sets inappropriately rigid assessment cutoffs for defective performance. Furthermore, data collection from neurologically normal subjects follows the same format as that used in the assessment of neurologically compromised subjects, while the more research oriented protocol used to collect normative data from volunteer participants does not.