This study suggested that carriers of MTHFR 677T allele were more likely to show an increased risk of autism than carriers of CC homozygotes (P = 0.004, OR = 1.18, 95% CI = 1.02–1.29), to some extent, which verifies that MTHFR may be one of the predisposing genes for autism. The gene discussed is MTHFR; the disease is autism.