Intervening with families is a promising strategy for addressing the continuing problem of adult and youth tobacco use. A four-step formative process was used to develop an innovative self-directed family-based intervention: (1) planning and strategy development through structured telephone interviews, a focus group, and a literature review; (2) development and pretesting of concepts, messages, and materials by using feedback from children and adults on prototypic materials; (3) implementing the program by mailing 6 modules to 50 families (composed of at least one adult smoker and a 9-12-year-old) with overall high levels of engagement; and (4) assessing effectiveness and making refinements by measuring the intervention effect on smoking-related communication, skills, and attitudes. Inconsistent intervention effects related to the difficulty of cessation and the influence of parental smoking suggested needed refinements. Engaging smokers willing to make a quit attempt during the intervention time frame may augment children's appreciation for the difficulty of cessation. Content related to stress management may need greater emphasis. Enhancing the personal context in which the influence of parental behavior is conveyed may be needed. Although the family context offers the opportunity to address the parent-child reciprocal nature of tobacco use, it requires sensitivity to the challenges of addressing this topic.