Diagnosing Asperger's syndrome (AS) in adults is difficult and efficient indicators for a precise diagnosis are important in the clinical setting. We examined the clinical characteristics of AS in 129 adults (median age, 32.0 years [range, 19-57]; 102 men and 27 women; AS group (n = 64; median age, 32.0 years [range, 19-50]; 50 men and 14 women), control group (n = 65; median age, 32.0 years [range, 19-57]; 52 men and 13 women) through administration of the Japanese version of the Autism-Spectrum Quotient (AQ) and the Japanese version of the Hospital Anxiety and Depression Scale (HADS), the Liebowitz Social Anxiety Scale (L-SAS), and the NEO Five-Factor Inventory (NEO-FFI). AQ, HADS, and L-SAS scores, and the "Neuroticism" scores of the NEO-FFI were significantly higher in adults with AS than in controls. The "Extraversion", "Agreeableness", and "Conscientiousness" scores of the NEO-FFI were significantly lower in adults with AS than in controls. Total score of the AQ correlated with the "Anxiety" subscale score of the HADS and the "Extraversion", "Openness", and "Conscientiousness" subscale scores of the NEO-FFI in adults with AS, but not in controls. The findings demonstrated that the AQ and other scales could be used to elucidate the clinical characteristics of AS in adults. (Contains 2 tables.)