We analyzed the performance of a two-stage screening protocol [the Modified Mini-Mental State Exam (3MS) or the Informant Questionnaire for Cognitive Decline (IQCODE), and the Dementia Questionnaire (DQ)] in a weighted stratified sample of 839 subjects from a population survey of dementia in Cache County, UT. The subjects were subsequently examined using a standardized diagnostic assessment protocol. Using the method of receiver operating characteristic (ROC) analysis, the main outcome measure was area under the ROC curve (AUC). The overall AUC estimates were 0.956 (95% confidence interval 0.943-0.968) for the 3MS/IQCODE and 0.945 (0.931-0.960) for the DQ. After adjustment for age, the efficiency of the both 3MS/IQCODE and the DQ was better for subjects with genotype epsilon4/epsilon4 at APOE, better among women, and better in those with two or more years duration of dementia. The optimal threshold for this two-stage screen yielded sensitivity and specificity estimates of 91.0% and 92.0%, respectively.