ABTRACT: Several clinical and biochemical variables were studied in 28 patients with arteriosclerotic brain disease (ABD) or senile dementia (SD) residing in the psychogeriatric service of a veterans' hospital with extended care facilities. The results did not provide any means of distinguishing between ABD and SD. Of special interest were: 1) the lack of any reliable difference in the serum cholesterol levels between the two groups of patients, and 2) the failure to find focal neurologic signs on clinical examination in both groups. Comparison of the patients with chronic brain syndrome (CBS) and normal elderly subjects indicated that the CBS patients weighed less, had higher preprandial blood glucose levels and lower levels of serum albumin and alpha-L, alpha-2 and beta globulin. Electroencephalographic abnormalities were much more common among the CBS group. No significant differences between our patients and normal elderly subjects were found with respect to blood pressure, serum cholesterol, creatinine, sodium, potassium, chloride, phosphorus, CO 2 combining power, osmolarity, total serum proteins, total serum globulin, gamma globulin, and the frequency of abnormalities in the electrocardiogram and in the intracranial and intrathoracic blood vessels.