We compared the screening accuracy of a short, five-item version of the Mental Health Inventory (MHI-5) with that of the 18-item MHI, the 30-item version of the General Health Questionnaire (GHQ-30), and a 28-item Somatic Symptom Inventory (SSI-28). Subjects were newly enrolled members of a health maintenance organization (HMO), and the criterion diagnoses were those found through use of the Diagnostic Interview Schedule (DIS) in a stratified sample of respondents to an initial, mailed GHQ. To compare questionnaires, we used receiver operating characteristic analysis, comparing areas under curves through the method of Hanley and McNeil. The MHI-5 was as good as the MHI-18 and the GHQ-30, and better than the SSI-28, for detecting most significant DIS disorders, including major depression, affective disorders generally, and anxiety disorders. Areas under curve for the MHI-5 ranged from 0.739 (for anxiety disorders) to 0.892 (for major depression). Single items from the MHI also performed well. In this population, short screening questionnaires, and even single items, may detect the majority of people with DIS disorders while incurring acceptably low false-positive rates. Perhaps such extremely short questionnaires could more commonly reach use in actual practice than the longer versions have so far, permitting earlier assessment and more appropriate treatment of psychiatrically troubled patients in primary care settings.