The Cancer Information Service's (CIS) nationally coordinated, regionally focused outreach program establishes partnerships with government, nonprofit, and private organizations to reach underserved and minority populations. A national random sample telephone survey, conducted with 867 partner organizations who had contact with the CIS in early 1996, assessed the types of CIS assistance used, satisfaction with and usefulness of these services, organizational characteristics, and the overall impact on partners' cancer-related programs. CIS partners provide programs for the medically underserved (79%) and specific racial and ethnic groups (72%) and address a range of cancer control issues. Partners use and highly value an array of CIS assistance. Over 90% are satisfied with the CIS services. Diffusion of accurate and science-based information, materials and resources is a key element of the outreach assistance. Two out of three partners are receiving late-breaking news and scientific information from the CIS and 86% are disseminating it to their constituents. The majority of those partners surveyed reported that they rely on the CIS to assist with their most important cancer programs. Sixty-eight percent of the partners rated the CIS assistance as important or very important to their cancer-related programs. These survey results indicate that the CIS outreach program provides key support to partners' cancer programs and has an impact on their efforts. The results support the effectiveness of a regionally based outreach program working in partnership with existing organizations at the state, county, and local level who are addressing the needs of underserved populations.