This study describes the development and usage of a Web-based component of a nutrition and physical activity behavioral intervention to promote bone health among preadolescent girls. Thirty Girl Scout troops were randomized to either an intervention or control group for a 2-year period. Girls in the intervention troops (aged 10 to 12 years, N=194) were exposed to grade-specific Web sites that were developed to reinforce the content of the broader, face-to-face intervention. In 5th grade, 82% of the girls logged on once and 48% logged on more than once, compared to 56% and 23% of 6th graders, respectively. Results suggest that although Web-site usage decreased over time, a Web-site program may be useful as a component of a face-to-face, multicomponent intervention. More research is needed to determine ways to enhance and maintain Web-site use over time among youth in health-behavior intervention programs.