As health communicators and practitioners continue to develop tailored health interventions, little is known about the most effective components and the underlying mechanisms through which tailoring effects occur. This project examines the role of theory in tailoring at promoting desired cognitive and behavioral outcomes in a mobile health intervention and whether dynamic tailoring bolsters the effect of tailored interventions. This project first systematically reviewed the current literature in mobile health intervention research to examine how mobile devices and various tailoring strategies are used. Results indicated that few mobile tailored health interventions examined the cognitive elaboration of the tailored messages. The project then conducted a between subjects 3 (behavior theory-based message v. non-theoretical tailoring v. combined) by 2 ( static tailoring v. dynamic tailoring) two-week field experiment, and found that the use of non-theoretical tailored messages could bolster the effect of theory-based messages at eliciting attitude and behavior change through increased cognitive elaboration and desired outcomes associated with behavior change theory. The findings also showed that implementing dynamic tailoring in mobile interventions did not produce additive effects. The project extends our understanding of the effective components contributing to tailored health interventions and the most efficient practices of using mobile technology and text messaging to improve health-related attitude and behavior chang.