A random sample of 182 elderly community residents and 211 demented patients were studied using the D-Test Battery based on the Luria's neuropsychological investigation method. A steady but selective cognitive impairment was observed with increasing age in normal healthy subjects. The most sensitive areas of cognition to the effects of normal aging were mnestic and conceptual functions, as well as arithmetical skills. The age-related changes could be clearly differentiated from the changes found in patients with mild degree of dementia. The test also differentiated patients with mild, moderate and severe dementia from each other on the basis of their social competence. It failed to demonstrate specific patterns of impairment and to clearly differentiate between patients with Alzheimer's disease and vascular dementia who had the same degree of cognitive decline. Further qualitative analyses are needed to improve the sensitivity and specificity of the test.