Objective: To investigate the role of chromosomal abnormalities and FMR1 gene variations in the etiology of Autism Spectrum Disorder (ASD). Methods: This clinical study included 80 patients who were referred to the Medical Genetics Department. Chromosome analyses and FMR1 fragment analysis methods were performed on DNA samples of these patients to detect any variations. The obtained data were compared with the literature data. Results: Eighty individuals were selected for this clinical study. In three patients, chromosomal abnormalities were found. No FMR1 gene defects were found in any of the patients. Conclusion: Chromosomal abnormalities were found in 3.75% of the patient population. This is compatible with literature data. The FMR1 gene was not found to be associated with etiology. According to these data, it is seen that chromosome analysis still has a valid place in explaining the genetic etiology of autism spectrum disorder.