Approximately one fourth of the estimated 1 million persons living with human immunodeficiency virus (HIV) in the United States are unaware that they are infected with HIV and at risk for transmitting the virus to others. In April 2003, CDC announced a new initiative, Advancing HIV Prevention: New Strategies for a Changing Epidemic, aimed at reducing barriers to early diagnosis of HIV infection and increasing access of persons infected with HIV to medical care and prevention services. A priority strategy of this initiative is to make HIV testing a routine part of medical care. In April 2004, HIV testing was implemented in one emergency department (ED) in Los Angeles, California, and one in New York, New York, to determine the feasibility and acceptability of offering rapid HIV testing as a routine part of health care in EDs. In January 2005, an ED in Oakland, California, also began offering HIV testing routinely. This report summarizes the preliminary results of integrating rapid HIV testing into the health-care services routinely offered in the three EDs during January 2005-March 2006. Those results indicated that, of 9,365 persons tested, 97 (1.0%) ED patients had newly diagnosed HIV infection, and 85 (88%) of those 97 were linked after diagnosis to HIV care and treatment. EDs should consider integrating rapid HIV testing into their routine medical services to identify patients who are unaware that they are infected with HIV and link them to health and prevention services.