In preparation for the 2008 Scholarly Communications Institute (SCI 6) focused on humanities research centers, the Council on Library and Information Resources (CLIR) commissioned a survey of digital humanities centers (DHCs). The immediate goals of the survey were to identify the extent of these centers and to explore their financing, organizational structure, products, services, and sustainability. The longer-term goal was to provide SCI 6 participants with a greater understanding of existing centers to inform their discussions about regional and national centers. The year-long study took place in two phases: (1) a planning phase during which a working definition of DHC was developed, selection criteria were established, candidates were identified, and methodology was planned; and (2) an implementation phase during which the survey was conducted and responses analyzed. Thirty-two organizations took part in the survey, which was conducted through interviews with senior management, and through Web site and literature reviews of the participating DHCs. The findings of this survey suggest that new models are needed for large-scale cyberinfrastructure projects, for cross-disciplinary research that cuts a wide swathe across the humanities, and for integrating the huge amounts of digital production already available. Current DHCs will continue to have an important role to play, but that role must be clarified in the context of the broader models that emerge. When one is investigating collaborative models for humanities scholarship, the sciences offer a useful framework. Large-scale collaborations in the sciences have been the subject of research that examines the organizational structures and behaviors of these entities and identifies the criteria needed to ensure their success. The humanities should look to this work in planning its own strategies for regional or national models of collaboration. Appendices include: (1) Sources for Survey Candidates; (2) Surveyed Organizations; (3) Survey Instrument; (4) Academic Departments Affiliated with DHCs in This Survey; (5) Bibliography; and (6) Tools for Humanists. (Contains 6 tables.)