The NCI-sponsored cooperative groups have made important contributions to improving treatment for many types of cancer, including breast, ovarian, colorectal, and childhood cancers. Cooperative group research has been instrumental in establishing innovative treatments that improve outcomes and quality of life. Despite these successes, the Cooperative Group Program has faced a number of challenges that threaten its effectiveness. To address this problem, the National Cancer Policy Forum (NCPF) convened a workshop titled "Multi-Center Phase III Clinical Trials and NCI Cooperative Groups" in Washington, DC, on July 1-2, 2008. The purpose of the workshop was to outline the challenges that the public clinical cancer research enterprise faces, and to identify possible solutions to these challenges.