Offering children with autism spectrum disorders (ASD) choices between activities (e.g., working on math or English), instructional materials (e.g., using a pen or pencil), or environmental arrangements (e.g., where to sit) has been shown to reduce challenging behavior maintained by escape from task demands. However, the majority of research investigating choice-based interventions for challenging behavior has examined across-activity choices (i.e., choosing between activities) and relatively few studies have examined within-activity choice (i.e., choosing between instructional materials or environmental arrangements). The purpose of this study is to replicate and extend previous research on choice-based challenging behavior interventions by comparing the effects of across-activity choices and within-activity choices on the escape-maintained challenging behavior of 4 children with ASD. An alternating treatment design was embedded within the "B" phase of an ABAB design in which the "A" phase represented a no-choice baseline condition. Both choice formats resulted in less challenging behavior than the baseline condition for all participants. Across-activity choice resulted in less challenging behavior than within-activity choice for 3 participants. Implications for research and practice are discussed.