Objective: With increasing frequency of autism spectrum disorder (ASD) in recent years, etiology has not yet been fully elucidated. Multiple hypotheses have been proposed to explain autism etiology including genetic, neurobiology-cal, psychosocial factors, environmental or iatrogenic causes. In this study, it was aimed to evaluate the relationship between OSB and RELN gene polymorphism. Methods: The present study included 62 children with ASD diag-nosed by DSM-5 criteria, aged between 3 and 12 years and 64 age and gender-matched healthy controls. Sociode-mographic Data Form was given in both groups and the Childhood Autism Rating Scale was administered to assess the severity of autism. Two single-nucleotide polymorphisms of reelin gene (rs1270519, rs362691) were genotyped using real-time PCR. Results: Of the 62 OSB cases included in the study, 57 were males (92%) and 5 were females (8%); of the 64 cases included in the control group, 52 were male (81%) and 12 were female (19%). The mean age of the patient group was 5.54±3.13, while the mean age of the control group was 6.43±4.04. There was no significant difference between the patient and control group in terms of sex and age. There was a statistically significant difference in rs1270519 polymorphism between ASD patients and healthy controls, but there was no significant differ-ence in terms of rs362691 between the two groups. Discussion: The results of this study show that the RELN gene rs1270519 polymorphism may be associated with ASD in the Turkish population. In order to clarify the relationship between ASD and RELN, there is a need for further studies that is evaluate other polymorphisms. [Anadolu Psikiyatri Derg 2018; 19(6.000): 599-606]