A review of hospital records was conducted for children evaluated for autism spectrum disorders who completed both the Leiter International Performance Scale-Revised (Leiter-R) and Stanford-Binet Intelligence Scales, 5th Edition (SB5). Participants were between 3 and 12 years of age. Diagnoses were autistic disorder (n = 26, 55%) and pervasive developmental disorder-not otherwise specified (n = 21, 45%). Analysis showed that the full sample received significantly higher scores on the Leiter-R than SB5 (mean discrepancy of 20.91 points), specific diagnosis was not a significant factor, and younger children had a larger discrepancy between tests. These analyses strongly suggest that the Leiter-R and the SB5 may not be equivalent measures of intellectual functioning in children with autism spectrum disorders, and that use of one or the other exclusively could lead to misclassification of intellectual capacity.