Objectives. Recent interventions report positive results following amulti-component campaign to increase stair climbing. This study investigated the effectiveness of volitional and motivational components of a stair-climbing intervention in the workplace. Design. Interrupted time-series design. Methods. Ascending stair/lift choices, coded by gender, were observed between 08:00-10:00 and 14:15-16:15 on weekdays, in four university buildings (n = 14,138; 46% female). Baseline observations (stage 1; 5 days) preceded a motivational intervention, that is, a poster positioned inside the lift(s), that was positioned in each building (stage 2; 5 days). Next a volitional intervention, that is, point-of-choice prompt, supplemented the motivational one (stage 3; 8 days). Logistic regression analysis of stair/lift choices included the independent variables of intervention components, gender, time of day, building height, number of lifts, and pedestrian traffic. Results. There was no significant change in stair climbing when the motivational component was positioned alone (Odds Ratio [OR] = 0.93, 95% Confidence Interval [CI] = 0.85-1.02, p = .123). In contrast, stair climbing increased significantly when the volitional component, that is, the point-of-choice prompt, was added (OR = 1.23, 95% CI = 1.14-1.32, p <.001). During both stages, building height, number of lifts, time of day, and pedestrian traffic were all associated with stair climbing. No significant gender effects were seen. Conclusions. A motivational component positioned alone, inside the lift(s) did not increase stair climbing. When a volitional component was added, that is, point-of-choice prompt positioned at the time and place where individuals choose their method of ascent, stair climbing increased significantly. Visibility of a prompt at the time behavioural choice is made appears necessary to change actual behaviour.