In the current study, the child AQ was administered in Japan, to examine whether the UK results for reliability and validity generalize to a different culture. Assessment groups were: Group 1: n = 81 children with Asperger Syndrome (AS) or high-functioning autism (HFA); Group 2: n = 22 children diagnosed PDD-NOS with average IQ; and Group 3: n = 372 randomly selected controls from primary and secondary schools. Both clinical groups scored significantly higher than controls (AS/HFA mean AQ = 31.9, SD = 6.93; PDD-NOS mean AQ = 28.0, SD = 6.88; controls mean AQ = 11.7, SD = 5.94). Among the controls, males scored significantly higher than females. The pattern of difference between clinical groups and controls was found to be similar in both countries.