Our findings were not sensitive to plausible variation in testing program characteristics, cost structures, discount rates, or health-related quality-of-life valuations. However, we found more favorable cost-effectiveness ratios when we assumed less background testing, higher HIV prevalence and incidence, and a greater impact of screening and treatment on secondary transmission, as measured by ΔR0 (initial values = −0.17, 0.00, and 0.17 in the favorable impact, no impact, and adverse impact scenarios, respectively). Figure 1 offers recommended HIV screening policies, assuming that society is prepared to pay up to $50 000 to purchase an additional QALY of health for its citizens. Undetected HIV prevalence in the screened population is the principal consideration in choosing to initiate a first screening. If it is assumed that antiretroviral therapy has no impact on secondary transmission, one-time screening is recommended for prevalences greater than 0.28%. With a favorable transmission impact (ΔR0 = −0.17), the lowest prevalence for which one-time screening is recommended falls to 0.20%; with adverse transmission impact assumptions (ΔR0 = 0.17), it rises to 0.40%. In formulating a policy for repeated screening, both the prevalence and incidence of HIV infection are important. For testing every 5 years (assuming favorable transmission impact), the threshold population has a prevalence of 0.45% for HIV infection and an annual incidence of 0.0075%.