Especially in outpatient settings, dementia is still an underdiagnosed syndrome. The Micro-Mental Test has been developed as a short version of the Mini-Mental-Status Examination (MMSE). We examined the reliability and diagnostic validity of a German version (Mikro-Mental Test). We administered the MMSE and the German version of the Micro-Mental Test to 20 inpatients of a geriatric psychiatry hospital (mean age 74.8+/-8.1 years), 55 patients from a cognitive clinic (mean age 71.9+/-9.1 years), and 27 healthy older adults (mean age 68.5+/-4.1 years). Diagnoses made by an experienced psychiatrist according to ICD-10 criteria served as external criteria. The mean duration for testing with the Micro-Mental Test was 8 min, and with the MMSE 15 min. Test-retest analyses showed satisfactory reliability. With regard to sensitivity and specificity, we found comparable diagnostic validity for the MMSE and the Micro-Mental Test. We suggest that, due to its brevity and diagnostic validity, the Micro-Mental Test is a useful tool for dementia screening in an outpatient setting.