The concept of intelligence and its representation by the Intelligence Quotient have been difficult to define and the subject of criticism for various reasons. Matarazzo and Kaufman have reviewed intelligence measurements and brain functions, but a biologically based explication of intelligence has not been explicitly proposed since the theories presented more than 40 years ago by Halstead and Hebb. The present study explored the overlap and differential sensitivity of intelligence measures (VIQ, PIQ, and FSIQ) and neuropsychological measures (Impairment Index and Category Test) to cerebral damage and educational attainment. The results indicated that neuropsychological measures may serve to broaden the concept of intelligence and that a brain-related criterion may contribute to a fuller understanding of its nature.