The terms 'testing' and 'screening' are defined as they refer to the enzyme-linked immunosorbent assay (ELISA) and supplementary tests. Proposed criteria for assessing mandatory population screening are presented. These focus on high reservoir of infection, significant risk of transmission, effective use of test results to reduce the spread of infection, critical consequences for the individual, and use of less intrusive means. Selected populations for screening include military personnel, school populations, patients at centers for the treatment of sexually transmitted disease and intravenous drug use, prisons, health care patients and staff, and premarital couples. Individual confidentiality and public health issues are discussed including duty to protect third parties and State reporting requirements. 239 footnotes.