This study sought to determine whether the augmentation of cognitive testing with an informant report questionnaire could improve accuracy in screening for dementia in a community setting. The sample consisted of 646 subjects aged 70-93 years. Cognitive state was assessed using the Mini-Mental State Examination (MMSE). Informants completed the 16-item short form of the Informant Questionnaire for Cognitive Decline in the Elderly (IQCODE). Dementia was diagnosed according to DSM-III-R criteria. Combination of the IQCODE with the MMSE resulted in more accurate prediction of caseness than either test alone. Receiver Operating Characteristic analysis demonstrated the superior screening performance of a logical "or" rule and a weighted sum of scores on the two tests over other methods of combination, replicating previous clinically based research. The findings also suggest that the appropriate combination of existing tests may be a fruitful method of improving screening accuracy in a variety of situations.