Antecedent exercise (AE) is an intervention used to promote moderate-to-vigorous physical activity and improve subsequent behavior in non-exercise contexts. We used withdrawal and multitreatment single case research designs to compare the effects of baseline, AE alone, and AE+visual supports condition. Two preschool-aged boys participated in this study. A masked secondary observer recorded interobserver agreement data for 100% of sessions; these data were continually monitored to detect biases. For one participant, AE alone was sufficient to reduce instances of challenging behavior during morning circle time. For the other participant, AE+visual supports was more effective than AE alone. These results point to the need for continued, rigorous research on the nuances of antecedent interventions for young children who demonstrate challenging behaviors. AE is but one such intervention requiring further investigation into for whom and under what conditions it might be effective. (author abstract)