The WAIS-R continues to be used on a widespread basis as a substitute for the WAIS in neuropsychological assessment, in spite of cautions that have been published (Bornstein, 1987). Although differences in results obtained with the two instruments have been reported, a feeling seems to exist that content differences between the two tests are minimal. This paper presents a detailed comparison of the subtests and reports that substantial differences in content are often present. Finally, our literature search failed to reveal a single study in which the WAIS-R has been shown to be sensitive to cerebral damage through controlled comparisons of brain-damaged and control groups. Sufficient evidence is not yet available to justify substitution of the WAIS-R for the WAIS in neuropsychological assessment.