The authors review the role of human immunodeficiency virus (HIV) testing in primary care, including an overview of epidemiologic trends of the HIV epidemic; avenues for HIV counseling and testing; HIV testing assays; guidelines for HIV test counseling in primary care; special situations involving testing of pregnant women, infants, and young children; post-exposure prophylaxis; and related resources available to Wisconsin primary care clinicians. HIV disease is a major cause of premature death and disability in the United States. Advances in the understanding of the pathogenesis of HIV and developments of newer antiretroviral therapies have resulted in dramatic changes in the management of HIV disease. Combination antiretroviral drug therapy has resulted in prolonged and near complete suppression of detectable HIV replication in many HIV-infected persons. These clinical developments underscore the importance of early identification and intervention in HIV disease. Intervention during primary HIV infection, the time when the viral burden "set point" is achieved, may present a special window of opportunity to effectively intervene in limiting viral replication in an infected individual. This earliest intervention may have major benefits for infected persons and society at large. Decreasing viral load during primary HIV infection may decrease an individual's infectiousness and thereby decrease the overall rate of transmission of infection to others. Primary care clinicians play a critical role in diagnosing, managing, and preventing HIV infection. Because of the ongoing relationship between patient and health care provider, the primary health care clinician is in the best position to provide HIV risk assessment, testing, related prevention education, and coordination of needed health care. This article presents guidelines for conducting HIV counseling and testing in primary care for purposes of furthering the public health objective of early identification of HIV infection. Clinicians can achieve this objective by including HIV risk assessment during the initial history and physical exam of every patient.