As of December 31, 2008, an estimated 663,084 persons were living with a diagnosis of human immunodeficiency virus (HIV) infection in the 40 U.S. states that have had confidential name-based HIV infection reporting since at least January 2006. Although HIV surveillance programs in the United States collect information about persons who have received a diagnosis of HIV infection and acquired immunodeficiency syndrome (AIDS), supplemental surveillance projects are needed to collect information about care-seeking behaviors, health-care use, and other behaviors among persons living with HIV.