Researchers associate an insistence on sameness or lack of behavioral flexibility with autism and Asperger syndrome, but few studies have sought to identify specific situations in which individuals insist on sameness. Along these lines, we developed the "Behavioral Flexibility Rating Scale" (BFRS) and conducted an Internet survey of parents of individuals with autism, Asperger syndrome, and Down syndrome. A total of 726 respondents submitted usable returns during the 3-month survey period. Parent report indicated that individuals with Asperger syndrome showed the most problems in relation to the insistence on sameness as measured by the BFRS, followed by individuals with autism and Down syndrome, respectively. When diagnosis was controlled, there were no gender or age differences. This preliminary investigation suggests that the BFRS may be useful in identifying specific situations associated with an insistence on sameness. Identifying specific situations in which individuals insist on sameness or show a lack of behavioral flexibility may be useful in planning interventions focused on promoting greater behavioral flexibility.