Clinicians often attach interpretive significance to high variability among subtest scores in IQ profiles of adults and children. In this study we evaluated the external validity of a relatively new measure of IQ subtest variability, the profile variability index (PVI). Within a sample of referred children, we administered the Kaufman Assessment Battery for Children, the Fourth Edition Stanford-Binet, and the Wechsler Intelligence Scale for Children-Revised. We calculated PVIs for each child from each test and correlated these values with achievement scores and indexes of discrepancy between actual and predicted scholastic achievement. Against these external criteria, PVI information from all three cognitive-ability batteries had essentially nil validity. We discuss implications of these findings for future research in this area.