Approximately one-quarter of a million persons in the United States who are infected with human immunodeficiency virus (HIV) do not know it. To decrease the number of such persons, primary care providers should make HIV testing a routine component of health care. HIV testing should also be offered routinely in other settings, such as emergency departments, jails, and substance abuse treatment centers. Currently, the Centers for Disease Control and Prevention and the Infectious Diseases Society of America recommend routine HIV testing only in settings where the prevalence of HIV infection is > or =1%; in settings where the prevalence of HIV infection is <1%, testing should be based on risk assessment. Because of the impracticality of strategies for testing that are based on estimates of prevalence, and because of the inaccuracy of risk assessment, we propose that HIV testing be routinely offered to any person who is sexually active. As an adjunct to the implementation of routine testing programs, counseling practices need to be streamlined, and rapid HIV testing needs to be implemented in the appropriate settings.