Addresses the role of implementation intentions (P. M. Gollwitzer, 1993) in promoting health-related behavioral change. Three behaviors are considered: breast self-examination, vitamin supplement use, and cervical cancer screening uptake. Vitamin supplement use and cervical screening uptake may each be regarded as primary prevention measures, serving to prevent disease; breast self-examination is a secondary preventive measure which serves to detect disease early in order to prevent severe consequences. The interventions were based on the Theory of Planned Behavior, which outlines the social cognitive processes underlying decisions to enact a given behavior and how an individual might be motivated to take up a new behavior. Results are reported from 3 experiments, showing that the formation of an implementation intention specifying where and when to perform the focal health behavior dramatically increased the likelihood of performance among positively motivated people. The fact that this effect was obtained across 3 different behaviors, using both self-report and objective behavioral indices, and among both student and general populations, confirms the generalizability of the findings to related health behaviors.