This investigation provides internal consistency reliabilities for Wechsler Intelligence Scale for Children--Fourth Edition (WISC-IV) subtest and index discrepancy scores using the standardization sample as the data source. Reliabilities range from 0.50 to 0.82 for subtest discrepancy scores and from 0.78 to 0.88 for index discrepancy scores. Thus, the reliabilities of the WISC-IV subtest and index discrepancy scores do not reach the 0.90 criterion recommended for clinical decision making. However, 5 of the 66 subtest and 33 of the 36 index discrepancy score reliabilities are 0.80, which is regarded as adequate when hypothesis generation is the goal instead of decision making. (Contains 2 tables.)