Background: Symptom overlap between autism spectrum disorders (ASD) and social anxiety disorder has been reported. However, few reports exist on the associations between autistic traits and social anxiety in young adults. Methods: Autistic traits and social anxiety were assessed using the Autism-Spectrum Quotient (AQ) and the Liebowitz Social Anxiety Scale (LSAS), respectively. The survey was performed as part of the student health check-up at admission to our school, Kochi University. The relationship between the AO and LSAS scores were analyzed. Results: In all, 1479 students (77.2%) completed both the questionnaires. The overall AQ score was significantly related to the score on the Japanese version of the LSAS (LSAS-J) (Spearman's correlation coefficient
0.46, p &lt
0.001). The group of students with AQ ≥ 33 had significantly higher total and subscale scores on the LSAS-J as compared to the group with AQ &lt
33, while the group with LSAS-J ≥ 44 showed significantly higher scores on all the subscales of the AQ, except "Attention to detail," as compared to the group with LSAS-J &lt
44. Conclusions: The results suggest that both students diagnosed as having ASD and those with autistic traits may experience anxiety symptoms. The score for "Attention to detail" on the AQ, which was not related to the presence of social anxiety, may be useful in discriminating between autistic traits and social anxiety.