Although a great number of psychometric tests and rating scales for the assessment of psychogeriatric patients is available, there is still an urgent need, in research and practice, for a clinical rating instrument that meets the following main requirements: (1) applicable to institutionalized and community patients and covering a wide range of behavioral pathology; (2) acceptable and easy to use for professionals and lay persons alike; (3) covering a wide range of behavior relevant to daily functioning but independent of sex or social status of the individual assessed. The NOSGER contains 30 items of behavior, each rated on a 5-point scale according to frequency of occurrence. Item scores are summarized into 6 Dimension scores (memory, instrumental activities of daily life, self-care, mood, social behavior, and disturbing behavior) which are clinically relevant in dementia, depression, and other psychiatric disorders of old age. Validation studies with a preliminary version of the NOSGER indicated good acceptance of the scale, high inter-rater and test-retest reliability, and high correlations of all NOSGER Dimension scores with results of a variety of established assessment instruments. The NOSGER is currently being used in a number of European and North American centers and should turn out to be a useful instrument for longitudinal studies in psychogeriatrics.