Since passage of the National Cancer Act in 1971, the NCI Centers Program has promoted the establishment and the development of cancer centers of many types throughout the nation. These now include 20 comprehensive cancer centers, as well as a number of clinical and basic science centers that are supported through NCI core grants. Scientific productivity at NCI-supported centers has been high. While cancer center core grants usually represent only a small proportion of the total extramural research support for a given institution, they are essential in providing shared resources and in pulling together the various component research programs of a center into a unified program. The future directions of the NCI centers program as a whole, as well as the role of cancer research centers within their communities and regions, are discussed.