Repetitive behaviors such as excessive straightening are commonly observed among individuals with autism. Attempts to prevent these behaviors may increase the likelihood of other problem behaviors. The present study was designed to assess and treat the excessive straightening and associated destructive behaviors of a 16-year-old boy who had been diagnosed with autism and moderate mental retardation. Following a series of functional analyses, an intervention that incorporated functional communication, extinction of destructive behavior, and blocking of repetitive straightening was demonstrated to be effective in reducing straightening and destructive behavior. (Contains 1 figure.)