<p>  In the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev., DSM-IV-TR), "borderline intellectual functioning"is defined as an intelligence quotient (IQ) ranging from 71 to 84. Few studies of individuals with borderline intellectual functioning have been published; the participants in published studies were mainly students who needed some clinical support in a school setting. In the present study, data on students were obtained from child guidance centers. The students were divided into 2groups, based on their scores on the Wechsler Intelligence Scale for Children -Fourth Edition (WISC-IV), in order to examine selection bias. Students in the borderline intellectual functioning group (n=295) were 195 boys and 100 girls, 8 years old or older. Students in the comparison group (n=262) were 154 boys and 108 girls whose IQ ranged from 86 to 99. The 2 groups were compared with simulated data (n=1,285) generated on the basis of the WISC-IV norms. The correlation matrix of the 10 WISC-IV subtests showed a selection bias in the borderline intellectual functioning and comparison groups, due to the restricted range of IQs. Multi-group analyses, however, confirmed the metric invariance among the borderline intellectual functioning, comparison, and simulated groups on the correlated 4-factor model as described in the WISC-IV manual. These findings suggest that the WISC-IV may be useful for measuring the intelligence of students with borderline intellectual functioning equivalent to typical students, although the correlation coefficients of the subtest data of the children with borderline intellectual functioning were lower, due to selection bias, than were the correlation coefficients of the simulated norm group. The discussion concludes that the factorial invariance found in the present study suggested that these findings may be fundamental for intelligence testing, and also may contribute to applied psychometrics.</p>