For this study, European WAIS III performance subtest norms were compared to the original US norms. When European WAIS III raw scores were scored using US norms, the resulting perceptual organization index (POI) means were significantly higher than the processing speed index (PSI) means. The POI/PSI difference is roughly 5-10 points for the German (n = 1897), Spanish (n = 1369), French (n = 1104), British (n = 370) and Finnish (n = 446) WAIS III standardization samples. The POI mean was higher than the PSI mean in all age groups in each European sample. It is concluded that cross-national differences in any one factor (such as general intelligence) are unlikely to cause such effects. It is hypothesized that cultural factors, differences in education and test-taking attitudes, underlie the difference between US and European test profiles. The results of the study suggest that national test norms may have poor cross-national validity even when the effects of age, sex and education are controlled for. (Contains 3 tables.)