Childhood cancer survivors represent a large and growing group who are at increased risk for developing subsequent cancers. Therefore, it is of critical importance that all preventable risk factors be minimized among this population. Of particular concern is that childhood cancer survivors who smoke are less likely to quit compared to the general population. To date, however, there have been no published smoking cessation studies targeting childhood cancer survivors. Evaluation of interventions that have the potential to reduce smoking prevalence among survivors are greatly needed. The proposed study will evaluate the impact of an innovative intervention that includes peer-delivered telephone counseling on smoking cessation for childhood cancer survivors. A randomized controlled design will be used in which individuals will be assigned to either a peer-delivered telephone counseling intervention or a self-help condition. Study participants will be drawn from the national Childhood Cancer Survivor's Study, a large cohort study of 20,000 childhood cancer survivors. The peer-delivered telephone counseling intervention includes: (1) a letter from a health care provider recommending that the patient quit smoking, and a self-help manual; (2) a series of six telephone counseling calls intended to enhance self-efficacy, reduce barriers, set goals for behavior change, and provide feedback concerning progress in achieving behavior change goals; and (3) tailored self-help materials addressing patient-specific barriers to change. The self-help condition includes a letter from a health care provider recommending that the patient quit smoking, and a self-help-manual. Differences in primary outcomes will be assessed through prospective surveys using validated measures. This study builds on our work in motivational and peer-delivered interventions and is strongly grounded in theoretical perspectives on health behavior change. Reduction of smoking prevalence among childhood cancer survivors is an important public health issue. This study will make significant contributions toward the development of effective smoking cessation interventions for high-risk populations and may serve as an important model for future cancer prevention intervention efforts.