Dietary interventions in the treatment of autism spectrum disorders (ASDs) are prominent in the media and among families of children with autism. One such intervention is a diet free of gluten (predominantly found in wheat products) and casein (found in dairy products), referred to as a GFCF diet. However, the efficacy of the GFCF diet in improving behavioral symptoms of autism has not been determined. A large-scale, multi-site, randomized controlled trial will be needed to evaluate the impact of this diet in children with autism. As an initial step towards such a complex and costly trial, this study aims to survey parents and key child health professionals in the United Kingdom to investigate their attitudes towards the use of the GFCF diet, and their preparedness to support a large-scale randomized controlled trial. These survey findings will determine what might help or hinder this research, and provide important general insights as to how to recruit and retain parents and professionals to studies addressing ASDs. These findings will be useful in designing and carrying out both research into the dietary treatment of ASDs, and other research into complementary and alternative therapies.