BACKGROUND. Innovations to improve the delivery of pediatric preventive care are needed. METHODS. We enrolled children, 0 to 11 years of age, into a factorial, randomized, controlled trial of a tailored, evidence-based, Web site (MyHealthyChild) that provided information on prevention topics before a scheduled well-child visit. There were 2 components of the intervention, namely, parental Web content and provider notification. Parental Web content provided information to parents about prevention topics; provider notification communicated to physicians topics that were of interest to parents. We assigned 887 children randomly to 4 groups (usual care, content only, content and notification, or notification only). Outcomes were determined with telephone follow-up surveys conducted 2 to 4 weeks after the visit. Poisson regression analysis was used to determine the independent effects of each intervention on the number of topics discussed and the number of preventive practices implemented. RESULTS. Parents in the notification/content group and in the notification-only group reported discussing more MyHealthyChild topics with their provider. Parents in the notification/content group and in the content-only group reported implementing more MyHealthyChild topic suggestions (such as use of a safety device). CONCLUSIONS. A Web-based intervention can activate parents to discuss prevention topics with their child's provider. Delivery of tailored content can promote preventive practices.