WISC and WISC-R subtest and IQ scores were compared in two samples of juveniles referred to a large metropolitan juvenile probation department (Ns = 180 and 185, respectively). The samples were equated for age, sex, race, and grade level. Significant differences were found on six of the 10 subtests. There were also significant differences between WISC and WISC-R scores on the Verbal, Performance, and Full Scale scores. In each case the WISC-R score was lower than the WISC score with the exception of the Arithmetic subtest. We conclude from these data that juvenile delinquents score significantly lower on the WISC-R than on the WISC. Psychologists using the WISC-R where the WISC had been previously used should educate their referral sources and other users of scores from the WISC-R to the differences in the test scores between the WISC and WISC-R.