Objective: Determine the temporal and spatial characteristics of stairs versus elevator use in a university residence hall to inform future physical activity promotion efforts. Participants: All residents and visitors for a single, four-story residence hall dormitory building located on a college campus in Orange, CA. Methods: Smart mat systems capable of detecting pedestrian traffic were placed in front of the stairs and elevators on each floor plus a basement. Generalized additive mixed models (GAMMs) were used to compare stair versus elevator usage at different times of the day and on different floors. Results: Stair versus elevator use varied much more throughout the day on floors nearest to the ground floor, with stair use most common in the morning. Overall, the elevator was used more frequently on higher floors, with less variation throughout the day. Conclusion: To be most effective, future stair promotion interventions should target residents on higher floors and in the morning.