6634 Background: Advertising in most medical journals is dominated by pharmaceuticals in part due to journal policy. This is primarily a fiscal consideration. Because advertising clearly influence physicians’ prescribing pattern, an indirect conflict of interest exists and may potentially affect patient care. The objectives of this study were to evaluate the extent of advertising in leading hematology-oncology (HO) journals published in the U.S. and to compare the findings to those of multi-specialty journals. Methods: We evaluated the following high impact journals that publish original research and included all issues issued in 2006: Journal of National Cancer Institute (JNCI), Journal of Clinical Oncology (JCO), Blood, New England Journal of Medicine (NEJM), Journal of the American Medical Association (JAMA), and Annals of Internal Medicine (AIM). Of these, only JNCI (currently not affiliated with U.S. NCI) is not owned by a medical society. The number and nature of advertising for each journal were collected. Results: There was an average of 84, 283, and 459 pages for each issue of JNCI, JCO, and Blood, respectively. Overall, HO journals allocated 20% (range, 8–32) of their pages for advertising. JCO had the most, while JNCI the least, advertising, both classified (6% vs 1% vs 1%; P = 0.001) and non-classified (26% vs 10% vs 7%; P = 0.001). Among non- classified advertising, the major categories were drugs (48.5%), journal information (14.1%), conference announcements (10.1%), research/clinical trial (7%), disease information (6.4%), continuing medical education (3.6%), and others (10.3%). Among journals, JCO had the most drug advertising (72.5%), followed by Blood (65.6%), while JNCI did not have any (0%). Compared to multi-specialty journals, HO journals had less amount of classified (3% [range, 1–6] vs 15% [range, 10–19]; P = 0.001) and non-classified (17% [range, 7–26] vs 21% [range, 18–25]; P = 0.001) advertising. Conclusions: While less than their multi-specialty counterparts, HO journals allocated a substantial proportion of their pages to advertising, the overwhelming majority of which were sponsored by pharmaceutical companies. The extent of advertising varied by journal, but was most prominent with JCO. Notably, JNCI did not have any drug advertising. No significant financial relationships to disclose.