OBJECTIVE: Universal HIV screening is recommended but challenging to implement. Selectively targeting those at risk is thought to miss cases, but previous studies are limited by narrow risk criteria, incomplete implementation, and absence of direct comparisons. We hypothesized that targeted HIV screening, when fully implemented and using maximally broad risk criteria, could detect nearly as many cases as universal screening with many fewer tests. METHODS: This single-center cluster-randomized trial compared universal and targeted patient selection for HIV screening in a lower prevalence urban emergency department. Patients were excluded for age (<18 and >64 years), known HIV infection, or previous approach for HIV testing that day. Targeted screening was offered for any risk indicator identified from charts, staff referral, or self-disclosure. Universal screening was offered regardless of risk. Baseline seroprevalence was estimated from consecutive deidentified blood samples. RESULTS: There were 9572 eligible visits during which the patient was approached. For universal screening, 40.8% (1915/4692) consented with 6 being newly diagnosed [0.31%, 95% confidence interval (CI): 0.13% to 0.65%]. For targeted screening, 37% (1813/4880) had no testing indication. Of the 3067 remaining, 47.4% (1454) consented with 3 being newly diagnosed (0.22%, 95% CI: 0.06% to 0.55%). Estimated seroprevalence was 0.36% (95% CI: 0.16% to 0.70%). Targeted screening had a higher proportion consenting (47.4% vs. 40.8%, P < 0.002), but a lower proportion of ED encounters with testing (29.7% vs. 40.7%, P < 0.002). CONCLUSIONS: Targeted screening, even when fully implemented with maximally permissive selection, offered no important increase in positivity rate or decrease in tests performed. Universal screening diagnosed more cases, because more were tested, despite a modestly lower consent rate.