The role of some genes and their single nucleotide polymorphisms (SNPs) as genetic contributors of complex diseases is still a topic of much investigation. Research on genes related to autism susceptibility has been somewhat challenging, but also promising. Common genomic variants of CNTNAP2 have been associated with autism, and a range of autistic phenotypes such as impaired language function, abnormal social behavior, intellectual deficiency, epilepsy, and schizophrenia have been associated with this gene. Earlier findings have suggested that SNPs in the CNTNAP2 gene may be used as genetic markers for predisposition to autism spectrum disorder (ASD). We analyzed the SNPs (rs7794745 and rs2710102) in the CNTNAP2 gene of 210 individuals with idiopathic ASD and 200 non-autistic individuals by polymerase chain reaction-restriction fragment length polymorphism. The results revealed higher frequency distributions statistically significant (P = 0.034) of the homozygous SNP rs7794745 (presumed risk genotype) in ASD patients as compared with control subjects. The results also showed an association (OR = 1.802, 95%CI = 1.054-3.083, P = 0.042) between the same homozygous genotype and ASD, suggesting that it is a susceptibility factor for autism in this Brazilian population.