Neugebauer R, et al. - The purpose of this trial was to comparatively assess the effectiveness of 5-fluorouracil and imiquimod in reducing the risk of subsequent actinic keratosis (AKs) in a large, integrated health-care delivery system in Northern California. The inference drawn was that 5-fluorouracil was substantially more effective than imiquimod in the short-term, but not long-term, prevention of subsequent AKs.