Functional analysis procedures are an assessment tool used to identify the antecedents that evoke problem behavior and the reinforcers that maintain such behavior. In the clinic-based environment there are limitations with replicating a natural environment where problem behaviors typically occur. For example, use of an analogue setting may produce false negatives (i.e., when no identifiable function is identified for a behavior, but for which a social function exists) at a greater rate than in the natural environment. In the current study, problem behaviors (i.e., tantrumming, self-injurious behavior, and perseverative speech) were assessed in both clinic and natural contexts, and a treatment was developed to address problem behaviors occurring in the natural environment. Assessment in the natural environment suggested that problem behaviors were evoked by restricted access to tangible items and likely maintained by attention and access to those items. The purpose of this study was twofold: First, following a false negative functional analysis result in the clinic setting, the perseverative speech and other problem behaviors of a 15-year old young woman with autism were evaluated in a natural setting to determine whether the variables in the natural setting would evoke problem behavior. The second purpose of this study was to develop a function-based treatment that could be applied and practiced in the natural setting in an attempt to decrease perseverative speech and other problem behaviors.