The prevalence of classic autism and autism spectrum disorder (ASD) appears to be on the rise, and to date, there remains no clear etiology or cure. Out of desperation, many families are turning to new therapies and interventions discovered through various media sources and anecdotal reports from other parents. Unfortunately, many of these newer, well-publicized interventions have little empirical support. One of the most popular yet currently scientifically unproven interventions for ASD is the gluten-free, casein-free (GFCF) diet. Clinicians working with families of individuals with ASD are often asked for advice and find themselves unable to offer the most up-to-date and scientifically credible information. This article provides an overview of ASD and the GFCF diet, a summary and critique of current research findings, recommendations for future research, and practical advice for families to use in deciding if a trial of the GFCF diet is in the best interest of their child and family.