Boucher et al. obtained in the Oswego study (Stewart et al. 2003b, 2008). These results outline the rele­ vance of assessing cohorts until late childhood and adolescence. In two cohort studies (Netherlands and Michigan), impairments associated with pre­ natal PCB were more salient in non­ breastf­ ed and/or in more socioeconomically disadvan­ taged children. Thus, some of the findings reported in this literature review might hold only for more vulnerable subgroups. It is pos­ sible that optimal child stimulation can help compensate for subtle brain insults related to PCB exposure (Jacobson and Jacobson 2004), decreasing the likelihood of observ­ ing significant effects in more advantaged subgroups of the population. Failure to con­ trol for the appropriate vulnerability factors might also explain the negative findings from some studies. For instance, both studies that did not find effects on IQ (CPP and North Carolina) did not control for quality of par­ enting as measured by quality of home envi­ ronment and parental verbal abilities. These variables were included in the analyses from the Michigan (11­year assessment), Oswego, Netherlands, and Germany cohort studies, all of which found significant effects. We can­ not rule out the possibility that the CPP and North Carolina studies could have found PCB effects among more disadvantaged chil­ dren in those variables. Particular attention to this issue should be given in future studies when reporting results. The CPP and North Carolina studies were the only two studies to use multiple testers at multiple sites. This could have caused increased variability in test­ ing procedures, resulting in poorer reliability and reduced sensitivity of the measures. The results of the present work can be used for the appropriate selection of neuro­ psychological tests in future studies of cohorts exposed to PCBs (or other similar organochlo­ rine compounds). With the objective of cor­ roborating the effects observed in birth cohort studies, we suggest that future studies sys­ tematically include the Fagan Test of Infant Intelligence (Fagan and McGrath 1981) dur­ ing infancy and the Continuous Performance Test (Conners 1995; Letz and Baker 1988) from childhood. These tests have been found to be sensitive to the neurotoxic effects of PCBs on several occasions. Other tests of EFs, such as those from the Delis­Kaplan Executive Function System (Delis et al. 2001) or Go/No­go tasks, and tests requiring pro ­ cessing speed, like the Coding subtest of the Wechsler Intelligence Scales (Wechsler 1991), might also be sensitive to the presence of PCB effects. Further investigation of attentional and verbal/phonologic processes could also reveal pertinent information about the nature of the effects of prenatal PCB exposure. Subtests from neuropsychological assessment 14 batteries used with children could be useful to this end. Among others, the Test of Everyday Attention for Children (TEA­Ch; Manly et al. 1999) battery is particularly well suited to disentangle processes required to perform attentional tasks, and the NEPSY (Korkman et al. 1998) battery has interesting subtests of phonologic processing. We also suggest that if statistical power is high, analyses should be performed for every subtest rather than only for global indexes, especially if using test batter­ ies such as the Wechsler Intelligence Scales for Children (WISC; Wechsler 1991), the MSCA (McCarthy 1972), and the Kaufman Assessment Battery for Children (K­ABC; Melchers and Preus 1994; Neutel et al. 1996). This could be accomplished with the existing data from the German and the Dutch cohorts, notably. Moreover, when using the Digit Span subtest (e.g., Wechsler 1991), analyses for both forward and backward conditions should be performed, because the processes involved for these conditions are qualitatively different. Even though such an approach increases the likelihood of making type 1 errors, it allows for appropriate comparison of results across stud­ ies and provides a better profile of the nature of the effects. Finally, the use of complementary meth­ ods for neuropsychological assessment would be advantageous for the study of the neuro­ toxicity of PCBs and related compounds. The understanding of the brain mechanisms involved in the production of specific cogni­ tive impairments would be improved with structural and functional brain imagery stud­ ies. Event­related potentials could increase our understanding about the specific aspects of cognitive function that are impaired by permitting the child’s performance to be eval­ uated for specific components arrayed across time. Such direct measures of brain activ­ ity are also less subject to bias by cultural, language, and socioeconomic factors. In summary, this review supports the existence of specific, detrimental effects of prenatal exposure to environmental levels of PCBs on neuropsychological functioning in children. EF impairments were mainly outlined. Failure to assess this specific aspect of cognition may explain why some studies did not find significant relationships between prenatal PCB exposure and cognitive devel­ opment. These effects, along with possible slower information processing and impair­ ments in verbal abilities and visual memory, can be responsible for the IQ effects observed in most studies. Ref Rencs Barkley RA. 1997. 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