This article highlights trends that show the influence of age, education, IQ, gender, and alcohol abuse on Halstead-Reitan Neuropsychological Test Battery (HRB) performance. These factors must be considered as possible competing hypotheses that might account for a patient's HRB performance. HRB scores among normal, community-living persons can resemble scores of individuals with known neuropsychological impairment due only to the effects of these variables. Accordingly, when clinical neuropsychologists use "levels of current performance" or research based "cut-off score" methods to make inferences about the adequacy of brain function, appropriate comparison norms must be used to minimize the likelihood of false-positive errors. This paper summarizes and provides references to some of these comparison norms. Additionally, robust estimates of premorbid ability are essential when one is making neuropsychological inferences. Such estimates can be obtained from nationally standardized measures of intellectual ability found on most grade and high school transcripts, as well as Scholastic Aptitude Test, military, and related aptitude test scores, plus the individual's social and occupational history. 14 to 33% of the variability between mean HRB scores in their comparison of one group of 50-to 62-year-olds to a second group of 67-to 86-year-olds. Their sample of normal, community volunteers included both males and females, but was rather small (n = 30) and of relatively high education (M = 14 years, SD = 2.4). Other studies that have reported correlations between age and HRB performance in apparently neurologically intact individuals have found results similar to those of Bak and Greene. Specifically, Vega and Parsons (1967) found that age accounted for 7 to 40% variance in HRB performance among their hospitalized, medical, and psychiatric control sample of 50 15to 74-year-old men and women with a mean age of 40.8 years (SD = 13.1). Similarly, Prigatano and Parsons (1976) found that age accounted for 18 to 59% variance in HRB performance among their hospitalized psychiatric control sample of 25 16-to 61-yearold men and women with a mean age of 33.2 years (SD = 15.8). Heaton, Grant, and Matthews (1986), in an impressively large and comprehensive study of demographic variables that affect HRB performance, documented that age accounted for half of one percent to 31% of the variance in HRB performance among their 553 "normal controls" of 15-to 81-year-old men and women with a mean age of 39.3 years (SD = 17.5). Interestingly, Yeudall, Reddon, Gill, and Stefanyk (1987) did not find an association between age and HRB performance that was as clear, or as strong, as indicated by these