Communicating evidence-based information that encourages patients and their physicians to make medical decisions based on “best evidence” remains a policy challenge, particularly in areas in which scientific risk information is limited or contested. Despite growing research on how decision-aids (patient guides, formal decision-tools and instructional media) affect treatment decision-making and patient satisfaction, little is known about how decision-aids are developed or disseminated. This comparative case study analyzes the process by which opinion leaders from patient advocacy organizations, professional groups and the American Association of Health Plans (AAHP) contributed to the development and dissemination of two nationally acclaimed evidence-based decision-aids for women with serious, life-threatening illnesses. The decision-aids, 1) High-Dose Chemotherapy with Bone Marrow Transplant for Metastatic Breast Cancer, A Patient Reference Guide and 2) Should I Enter A Clinical Trial? A Patient Reference Guide for Adults with a Serious or Life-Threatening Illness, were both published by ECRI, a non-profit research institute that is one of 13 institutions designated by AHRQ as an Evidence-Based Practice Center and a WHO Collaborating Center. This study analyzes: 1) the roles professional and patient advocacy organizations played in advising ECRI on the design, development and communication modalities for both decision-aids using the best available scientific evidence on risk and outcomes; 2) strategies used by professional compared to advocacy groups to disseminate the decision-aids; and, 3) indicators of the effectiveness of professional compared to advocacy groups for disseminating the decision-aids to patients and clinicians.