AbstractThe validity of Wechsler's (1949) comments concerning the addition of the supplementary WISC subtests was investigated for a sample of 20 fifth‐grade students. The study was designed like that of Engin (1974) which investigated whether or not the addition of one or both of the supplementary WISC sub‐tests, Digit Span and Mazes, materially affected the obtained IQs of high achieving fifth‐grade subjects. All 12 subtests of the WISC were individually administered to the students, and IQs were then calculated in such a manner that specific comparisons could be made. These comparisons were between verbal, Performance and Full Scale IQs composed of the maximum number of subtests, and verbal, Performance, and Full Scale IQs exclusive of Digit Span, Mazes, or both subtests. T‐tests for correlated means were employed and revealed highly significant differences. The addition of Digit Span and Mazes in the WISC battery served to depress the verbal, Performance and Full Scale IQs of the high achieving students. The study serves to validate the previous investigation by Engin