Among women, the epidemic of smoking related cancers continues to grow and lung cancer recently surpassed breast cancer as the leading cause of cancer mortality. Smoking cessation is a cornerstone of cancer prevention and control because cancer risk declines following smoking cessation. Unfortunately, relapse is the "rule rather than the exception" among smokers attempting to quit and relapse remains the most refractory aspect of nicotine dependence. Women appear to have higher relapse rates than men and relapse prevention has been identified as a priority in reducing smoking prevalence among women. Basic and clinical research on the precipitants of smoking relapse have demonstrated that coping behaviors are powerful determinants of relapse. The most influential model of smoking relapse, "relapse prevention" (Marlatt & Gordon, 1985), proposes that self-efficacy and outcome expectations are causal determinants of coping behaviors, and in fact, these variables have been among the better predictors of relapse. Moreover, there is evidence that interventions based on relapse prevention theory are effective, that they instill coping skills, and that coping skill acquisition mediates intervention effects on abstinence. The specific aims of this proposal are to: l) Develop and evaluate the efficacy of a unique, self-help smoking relapse revention intervention among women. The intervention will be administered via a small hand-held computer. The general ontent of the intervention will be tailored specifically for women and each participant's intervention will be individualized prior to delivery based on state-of-the-art "ecological momentary assessment" techniques; and, 2) Examine the effects of the relapse prevention intervention on hypothesized treatment mechanisms (coping behaviors, self-efficacy, processes of change, negative affect, perceived stress) and the impact of those mechanisms on relapse, i.e. test for mediation effects. The proposal translates basic and clinical behavioral science research into a novel, theoretically-based treatment that provides individualized, situation-specific coping strategies, motivational and supportive messages, and other relapse prevention information. Moreover, unlike conventional relapse prevention treatments, participants have access to the intervention at an time and in any place, i.e. the intervention occurs in real-time in naturally occurring settings. The intervention has the potential to produce significant advances in the prevention of smoking relapse.