 Review of the literature concerning the effectiveness of gluten-free and casein-free diet GFCFD in individuals with ASD reveals a possible bias of the available studies and lack of a definite conclusion. Among 35 identified studies only two randomized controlled trials have been analyzed. The datainformation on reported effectiveness of interventions in the behavioral symptoms mean difference MD-mean difference -5.60, 95 CI -9.02 to -2.18, p 0.001 in Knivsbergs study, is not reliable because of study limitations. Whiteley et al summarized in 2012 the positive effect of GFCFD on various symptoms in ASD patients. However the influence of GFCFD in ASD children can be defined mostly as suggestive because of the methodological limitations. The main biases include: small sample size, unclear process of randomization and allocation, use of different ASD assessment tools, short trial duration, lack of evaluation of patients compliance to intervention, and other limitations. 