BACKGROUND: The rapid pace of genetics research, coupled with evolving standards for informed consent, can create ethical challenges regarding future use of tissue or information from completed clinical trials. The Cancer and Leukemia Group B (CALGB) Oncology Cooperative Group was faced with an ethical dilemma regarding sharing genetic data from a completed genome‐wide association study (GWAS) that was conducted as part of a large, multicenter breast cancer clinical trial with a national database: the Database of Genotypes and Phenotypes National Center for Biotechnology Information (dbGaP). METHODS: The CALGB Ethics Committee conducted a series of multidisciplinary meetings and teleconferences involving patient advocates, bioethicists, clinical researchers, and clinical oncologists to evaluate the ethical issues raised by this case and to identify lessons for improving informed consent to future genetics research in oncology trials. RESULTS: The Ethics Committee recommended that GWAS data be provided to dbGaP consistent with documented consent for future use of tissue among trial participants. Ethical issues, including adequacy of informed consent to future research, limitations of privacy in modern genetics research, the potential impact of population‐based genetics research on health disparities, and recontact of research participants for clinical care or further research, were identified as major ethical considerations in this area. CONCLUSIONS: Although modern standards for informed consent should not prohibit research or sharing of data consistent with participant's intent and the public interest, there is an urgent need for national consensus on the appropriate use of archived tissue and standardized informed consent for future research among cancer clinical trial participants. Cancer 2012. © 2012 American Cancer Society.