Purpose: The Children's Oncology Group (COG) strongly supports the widely recognized principle that research participants should be offered a summary of study results. The mechanism by which to do so in a cooperative research group setting has not been previously described. Methods: On the basis of a review of the available empirical and theoretic literature and on iterative, multidisciplinary discussion, a COG Return of Results Task Force (RRTF) offered detailed recommendations for the return of results to research study participants. Results: The RRTF established guidelines for the notification of research participants and/or their parents/guardians about the availability of research results, a mechanism for and timing of sharing results via registration on the COG public Web site, the scope of the research to be shared, the target audience, and a process for creating and vetting lay summaries of study results. The RRTF recognized the challenges in adequately conveying complex scientific results to audiences with varying levels of health literacy and recommended that particularly sensitive or complex results be returned using direct personal contact. The RRTF also recommended evaluation of the cost, effectiveness, and impact of sharing results. Conclusion: These recommendations provide a framework for the offering and returning of results to participants. They can be used by individual investigators, multi-investigator research collaboratives, and large cooperative groups.