The media are a frequent and sometimes sole source of cancer information for many people. News coverage of cancer can be influential to cancer-related practices such as prevention or detection behaviors, and sources cited by journalists may be influential in shaping this coverage. A content analysis (n = 3,656 stories) revealed that the most frequently cited sources in cancer news articles-research institutions and medical journals-receive disproportionately more attention compared to the National Cancer Institute (NCI), the American Cancer Society (ACS), and pharmaceutical companies. Research institutions were cited twice as frequently as medical journals, and more than three times as frequently as pharmaceutical companies. Most clinical trial stories were optimistic or neutral in tone, and tone was significantly related to citations of pharmaceutical companies and medical journals. Implications for effects of cancer coverage on behaviors, and the influence of sources such as research institutions and pharmaceutical companies, are discussed.