Background and purpose - In our study, we aimed to evaluate inflammation by measuring serum Adenosine deaminase and dipeptidyl peptidase IV levels of individuals diagnosed with autism spectrum disorder and to determine its relationship with the Childhood Autism Rating Scale. Methods - 37 children aged 2-12 years with a diagnosis of autism spectrum disorder and 27 children aged 2-12 years without any psychiatric disease were included in the study. Psychiatric examination and clinical evaluation according to DSM-5 diagnostic criteria for the diagnosis of autism spectrum disorder were performed on the children included in the study. The Childhood Autism Rating Scale was filled in by the researcher by interviewing the parents of the children diagnosed with autism spectrum disorder. 5 ml of venous blood samples were taken from the children in both groups in the morning on a full stomach. Results - There was no statistically significant difference between the groups in terms of age, gender, and sociodemographic data. While serum adenosine deaminase levels were found to be statistically significantly higher in the group with autism spectrum disorder, serum dipeptidyl peptidase IV levels were found to be significantly lower. A positive correlation was found between dipeptidyl peptidase IV and Childhood Autism Rating Scale. Conclusion - We think that inflammation may play a role in the etiology of autism spectrum disorder due to altered adenosine deaminase and dipeptidyl peptidase IV levels in children with autism spectrum disorder.