Diagnostic tests for human immunodeficiency virus (HIV) infection have undergone considerable evolution since the first enzyme immunoassay (EIA) and Western blot were introduced 2 decades ago. Newer methods detect infection sooner and yield results much faster. Rapid tests represent a major advance for HIV screening in the United States. Six rapid tests for detection of HIV antibody have been approved by the Food and Drug Administration (FDA) since November 2002. Four of these tests can be done in point-of-care and nonclinical settings because they use whole blood or oral fluid and are simple to perform. An assay for detection of HIV-1 RNA has been approved by the FDA to detect HIV infection before seroconversion has occurred and to confirm results of reactive screening tests; pooled testing of specimens for HIV-1 RNA has increased the cost-effectiveness of this screening tool. These new testing technologies offer unique opportunities to diagnose HIV infection among the estimated 252,000-312,000 persons in the United States who are currently unaware they are infected.