The Agency for Healthcare Research and Quality (AHRQ) Effective Health Care Program has issued two reports that examine when AHRQ should update comparative effectiveness reviews (CERs). The first document is a draft research review on "Updating Comparative Effectiveness Reviews". This guidance sets forth a framework for identifying new evidence or evidence not considered in a previous CER, how the update process will be used, and how new data will be incorporated. Comments will be accepted until October 19, 2009. The second document is a final report entitled "Assessment of the Need to Update Comparative Effectiveness Reviews: Report of an Initial Rapid Program Assessment (2005-2009)." This document assesses whether previous CERs need to be updated and prioritizes those CERs for review.