This research extends previous research regarding the intellectual functioning of autistic individuals on standardized measures of intelligence (Wechsler Adult Intelligence Scale-Revised and the Wechsler Intelligence Scale for Children-Revised). In Study I 33 individuals with autism who closely fit the DSM-III criteria were studied. Clear evidence was found that differentiates these individuals' verbal intellectual processes from their visual-motor intellectual abilities. Principal components analysis was used to examine the interrelationship among the various intellectual abilities which such tests of intelligence measure. In Study II the intellectual abilities of a group of autistic 8- to 12-year-olds were compared to age-matched groups of children with receptive developmental language disorder, dysthymic disorder, or oppositional disorder. The intellectual abilities of autistic children were significantly different from the other groups of children.