A factor-analytic study of the structure of intellectual functioning as measured by Wechsler tests was carried out on 4 samples of varying pathologies and 4 normal samples of varying ages. Applying objective analytical oblique rotation and statistical measures of factorial similarity, 3 main factors and 1 quasi-specific described most groups. In distinction to previous studies, both pathology and normal aging were found to introduce some degree of factorial variability, with the effect of age seemingly more pronounced. Thus, pathological samples did not differ from age-matched normals, though normals of different ages varied from each other. The results were discussed in terms of the relative importance of the different factors, process-reactive distinction in schizophrenia, and the particular vulnerability of the Memory factor. (PsycINFO Database Record (c) 2006 APA, all rights reserved)