This supplement was developed from a national meeting entitled "Opportunities for Improving HIV Diagnosis, Prevention & Access to Care in the U.S.," held 29-30 November 2006 in Washington, D.C. Leaders in the fight against human immunodeficiency virus (HIV) infection were recruited from areas of government, academia, clinical medicine, patient advocacy, and private industry to discuss the following ambitious topics: (1) strategies to significantly reduce overall HIV transmission rates in the United States, (2) methods to identify the estimated 250,000 individuals in the United States who remain unaware of their positive HIV serostatus, so they can be offered treatment earlier in the course of their disease, and (3) obstacles associated with opt-out HIV testing, including limits on resources for treatment of HIV infection. We served as cochairs for the meeting and, in conjunction with a scientific planning committee we appointed, oversaw the selection of the articles published in this supplement. Cumulatively, the articles address the stated topics by identifying methods to ensure the success of more-aggressive HIV testing measures, such as those described in the September 2006 recommendations of the Centers for Disease Control and Prevention; examining the success of current measures to prevent HIV infection such that future strategies can be improved; identifying the methods that will foster earlier diagnosis and access to treatment for individuals with HIV infection; and determining the limitations in human and financial resources to adequately care for a surge in the number of individuals with newly diagnosed HIV infection.