The Autism-Spectrum Quotient (AQ; Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001) has been recently developed to assess how individuals of normal intelligence vary on autistic traits. The main objective of this study was to assess the factor structure of the AQ in a large Scottish University sample (n = 536). G roup differences in the AQ were also assessed. The current study found four factors of 'Socialness', 'Pattern', 'Understanding Others/Communication' and 'Imagination'. Baron-Cohen, Wheelwright, Hill, Raste, and Plumb (2001) suggest five subscales, previous factor analytic Studies find two- or three-factor models. However, all agree on a 'Socialness', and a 'Patterns/Attention to Detail' factor. In addition, a 'Communication' factor is largely agreed upon. Group differences were as expected, students enrolled in a mathematical science degree type scored higher than other students, and males scored higher than females. The AQ, in a UK population, appears to be reasonably reliable, however. it does require some revision. (C) 2009 Elsevier Ltd. All rights reserved.