BACKGROUND: Congenital Toxoplasma gondii infection during pregnancy due to reduced maternal immune system could increase the risk of a child's autism disorder. OBJECTIVES: The aim of this study was to compare the Toxoplasma gondii infection in children with autism and normal children. METHODS: The research method was a case control study. The participants included 50 autistic children and 50 normal (N=100) children, aged between 3 and 12 years-old. They were matched according to age, socio-economic status, severity of the disorder, lack of physical and mental illness and other criteria considered in this research. From each group 5ml blood samples were collected to assess the prevalence of antibody against Toxoplasma gondii. To investigate the research hypotheses, the data were analyzed by Chi-square test. RESULTS: The results showed that children with autism had a higher level of frequency contamination with Toxoplasma gondii parasite infection than normal group (p < /em><0.001). CONCLUSIONS: Infection rate of Toxoplasma gondii in children with autism was significantly higher than in normal children.