OBJECTIVE: To develop a tailored, theory-based, Web-delivered intervention to prevent excessive weight gain in young adults using a Community-Based Participatory Research model. DESIGN: Investigators from 14 universities developed the intervention and supporting administrative portal using the 4 phases of the PRECEDE model. Steering committees were composed of the target audience (aged 19-24 years) and key health/wellness personnel were formed at each institution and provided information during each phase that was used to guide development of the intervention, Project YEAH (Young Adults Eating and Active for Health). Piloting results were used to refine the curriculum and identify and avoid barriers to delivery. RESULTS: Qualitative and quantitative data collected at each phase informed Project YEAH development. In Phase 1, factors of highest priority to young adults were identified. In Phase 2, environmental supports for healthful lifestyles were elucidated. In Phase 3, behavior and environmental changes considered important and changeable were identified. In Phase 4, the 10-week, theory-based, stage-tailored, interactive-learning intervention with a 10-month reinforcement period was developed. CONCLUSIONS AND IMPLICATIONS: Applying the PRECEDE model with fidelity during development of Project YEAH resulted in an intervention that pilot participants found relevant and useful, gained attention, instilled confidence in the ability to apply the information, and provided a sense of satisfaction.