Baron-Cohen, Wheelwright, Skinner, Martin, and Clubley (2001) constructed brief, self-administered instruments named the Autism-Spectrum Quotient (AQ), for measuring the degree to which an adult with normal intelligence has the traits associated with the autistic spectrum. In this paper, we report on a Japanese version of this new instrument. Three groups of Japanese subjects were assessed. Group 1 (n=57) consisted of adults with Asperger Syndrome (AS) or high-functioning autism (HFA). The other two groups were control groups. Subjects of Group 2 (n=194) were normal adults and those of Group 3 (n=1050) were students selected from five Universities in Tokyo and Chiba. The adults with AS/HFA had a mean AQ score of 37.9 (SD=5.31), which was significantly higher than the two control groups (Group 2: X=18.5, SD=6.21, and Group 3: X=20.7, SD=6.388). While eighty-eight percent of the adults with AS/HFA scored more than 33 points, only 3% of subjects in the two control groups indicated those points. Among the controls, males scored slightly but significantly higher than females. The reliability of the AQ in both test-retest and inter-rater measures were significantly high.