Using the Japanese version of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III), 26 girls with high-functioning (IQ greater than or equal to 70) pervasive developmental disorders (HFPDD) (mean age, 8.2 years) were compared with 116 boys with HFPDD (mean age, 9.0 years). Compared with the boys, the girls scored significantly higher on the Processing Speed index, Coding, and Symbol Search, but scored significantly lower on Block Design. Although both groups showed weakness on Comprehension in the verbal domain, the girls' subtest profile in the performance domain was relatively even and significantly different from the boys', which was characterized by a peak on Block Design. Such differences should be replicated, and possible behavioral, neurological, and genetic links to these sex differences should be clarified.