The Agency for Healthcare Research and Quality (AHRQ) is sponsoring the fourth symposium and webcast on methods in comparative effectiveness on 6/12-13/12 in Rockville, Md. The symposium will focus on original research and the methodological insights or advances that arise from conducting research. The AHRQ invites all DOs and other researchers to submit applications on such topics as prescription drugs, medical devices, invasive or non-invasive procedures, complex clinical strategies, health care delivery systems/improvement programs, and diagnostics. Preference will be given to work that represents innovative approaches to comparative effectiveness research and the challenges of effectiveness research. Complete information is available online.