Health behavior interventions may have different effects when targeting individuals at different stages of change. A 'motivation' stage, during which intentions are formed, has been distinguished from a 'volition' stage, implying that the latter requires self-regulatory effort in implementing and maintaining behavior. To test this stage assumption, an action control intervention (self-monitoring tool for dental flossing) matched to the volition stage and mismatched to the motivation stage was provided to 151 university students, with follow-up measures of action control and flossing after 2 and 6 weeks. Separate regression analyses for motivational and volitional participants indicated that only volitional participants benefited from the volitional intervention. This supports the usefulness of stage assumptions and the advantage of tailoring interventions to participants who reside either in the motivational or in the volitional stage.