Several good-quality studies of the cost-effectiveness of HIV screening have been published (24 - 28). A key variation among these studies is whether they consider preventing transmission of infection to others as one of the calculated benefits. One good-quality study showed that early identification and treatment resulted in an increase in life expectancy of 1.52 years in an HIV-infected patient, with a decreased benefit in older patients (27). The study suggests that a one-time screening program would reduce lifetime numbers of transmission from an average of 1.12 to 0.95, 0.35, and 0.12 partners among men who have sex with men, heterosexual men, and heterosexual women, respectively (27). The study found that screening was cost-effective (with a cost-effectiveness ratio of $50 000 per quality-adjusted life-year [QALY] gained), even at a prevalence as low as 0.05%. A study of the cost-effectiveness of screening among inpatients found that screening would be cost-effective at a prevalence of 0.1% (28). Another study that also did not include benefit from reduced transmission showed that the incremental cost-effectiveness of one-time screening was $36 000 per QALY gained in a high-risk population with a prevalence of 3.0%, $38 000 per QALY gained in a population with a prevalence of 1%, and $113 000 per QALY gained in the general U.S. population with a prevalence of 0.1% (25). More recent analyses that included the benefit from reduced transmission indicated that screening could be cost-effective at a prevalence as low as 0.2%, depending on the extent to which transmission is reduced (24). A study of targeted versus routine screening (29) concluded that targeted screening could prevent more HIV infections if accompanied by pre- and posttest counseling. The study, however, assumed that high-risk patients could be identified at no cost, an assumption that is at odds with the evidence that many high-risk individuals are not identified through targeted screening. Finally, a cost-effectiveness analysis of screening older patients found that screening would cost less than $60 000 per QALY gained in patients age 65 to 75 years at a prevalence of 0.1%, if patients had a sexual partner at risk and streamlined counseling was used (26). In summary, these cost-effectiveness analyses (24 - 28) provide good evidence that screening for HIV is cost-effective, even when prevalence is low, in the range of 0.1% to 0.2%.