OBJECTIVE: This study compared serum levels of S100B, GFAP, UCHL-1, NF-H and MMP-9 between children with Autism Spectrum Disorder (ASD) and controls, focusing on their association with regression in ASD. We hypothesized that neuroinflammation and neuronal/astroglial damage markers would be higher in the ASD group than in controls and even more elevated in the regressive ASD subgroup compared to the non-regressive subgroup. METHODS: The study included 50 children with ASD (ages 4-10) and 30 healthy children. Participants underwent the K-SADS-PL diagnostic interview, CARS, a semi-structured interview for regression, ABC, AuBC, CPRS-RS and SRS assessments. Serum levels of S100B, GFAP, UCHL-1, NF-H and MMP-9 were measured using flow cytometry and ELISA. RESULTS: Serum levels of S100B, GFAP, UCHL-1, NF-H and MMP-9 showed no significant differences between the ASD and control groups. Within the ASD group, no notable differences were found in sociodemographic, clinical characteristics, or serum marker levels between those with and without regression. CONCLUSION: The findings obtained in this study suggested that it is necessary to question whether the peripheral circulation can represent changes in central nervous system and to review the existence of autistic regression as a separate entity in ASD in terms of clinical features and etiopathogenesis.