A subset of 3 screening criteria (Q wave greater than or equal to 30 ms in lead aVF, any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV in lead V2, and R wave greater than or equal to 40 ms in V1) has been proposed to identify single nonacute myocardial infarcts. Cumulatively, these 3 criteria achieved 95% specificity, and 84 and 77% sensitivities for inferior and anterior myocardial infarcts, respectively, among patients identified by coronary angiography and left ventriculography. This study establishes the true sensitivities of the set of screening criteria in 71 patients with anatomically proven single myocardial infarcts and 32 patients with multiple myocardial infarcts. In the single inferior infarct group, the aVF criterion was 90% sensitive. The V2 criterion (any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV) was 67% sensitive in the single anterior infarct group. No single criterion proved sensitive in identifying a posterolateral infarct. The set of screening criteria performed just as well for multiple infarcts as it did for single infarcts, with a cumulative sensitivity of 72%. The overall sensitivity of the screening set in the 103 patients in all groups was 71%.