This study investigates the Geriatric Basis Assessment (GBA) in terms of its reliability. Data from 1037 patients were collected. The reliability was estimated relating to the lambda 2 coefficient. It is necessary to define the items in different categories: the first variable means valuation 1 of each item and not 2, 3, 4; the second variable means valuation 1, 2 against 3, 4; the third variable means the valuation 1, 2, 3 and not 4. The table shows only little difference concerning the lambda 2 coefficients. In conclusion, 80% of the variability of the GBA items can be explained by differences in the patients themselves, while 20% is due to the inaccurate assessment system. For 343 patients, data for both Barthel index and GBA were available. As presumed, correlations between Barthel and connected GBA items were observed. However, the correlations were too weak to predict the Barthel scores from the corresponding GBA item accurately enough. The Barthel index appears to include similar, but not exactly the same aspects as the GBA. The reliability of the Barthel index (lambda 2 = 0.89 for the first variable) is slightly higher compared to the GBA but it is not suitable as a criterion of validity. Both the validity of the GBA and the Barthel index can not be determined lacking an external measure. As an example, a suitable criterion of validity could be the reintegration into the familiar surroundings preceding the hospital stay. When developing the GBA, it was not assumed that geriatric patients could be correctly diagnosed on the basis of an overall score alone or to allocate them to adequate care using that score as a sole indicator. Crucial for these purposes is the test profile as a whole, including the impairments, disabilities handicaps, and last but not least the diseases of the individual patient. Furthermore, the depiction of the GBA profile at admission and discharge allows one to identify those items, on which therapy has a significant influence and those which remain more or less stable. As presumed, items with minor initial deficits (e.g., motivation, eyesight, hearing, depression, capability of verbal expression, situative adaptability, understanding) showed only small differences between admission and discharge. On the other hand, items strongly influenced by geriatric treatment were, e.g., mobility (walking, transfer), functions of internal medicine, and domestic care. Prognostically significant are those items which are crucial for reintegration and describe a deficiency but cannot be altered reliably. Such items are the person, to whom the patient relates most closely, situative adaptability, motivation, orientation, capability of verbal expression, and possibly depression. All of these parameters are more difficult to influence than the activities of daily living assessed by the Barthel index. Further investigations should clarify whether the GBA can be a reliable tool for allocating a patient to adequate care. However, the requirement for such a criterion of validity is that this allocation is truly optimal for the patient.