The Autism Spectrum Quotient (AQ) has been developed to measure the degree to which an adult with normal intelligence has autistic traits. In this paper it is evaluated for its potential as a screening questionnaire in clinical practice on one hundred consecutive referrals to a diagnostic clinic for adults suspected of having Asperger Syndrome or high functioning autism (AS/HFA). The results indicate that it has good discriminative validity and good screening properties at a threshold score of 26. The implications of these results are discussed.