We describe a Spanish adaptation and standardization of the Alzheimer's Disease Assessment Scale (ADAS) carried out as part of a prospective, coordinated study performed simultaneously in two Spanish health centers. Three diagnostic groups were defined: 21 healthy volunteers (normal group); 22 patients with cognitive deterioration but no dementia (CDND group); and 20 patients with Alzheimer type dementia (ATD group). The subjects were examined at the start of the study and after 3 and 6 months. The mean cognitive ADAS scores were significantly different in the 3 groups (F = 67.2, p = 0.0001), as follows: normal group, 7.6 +/- 2.1; CDND group, 12.4 +/- 4.5; and ATD group, 21.0 +/- 4.7. Likewise, the ADAS proved sensitive to the course of deterioration in the ATD group, while the other groups' scores improved. We conclude that the ADAS, and in particular the cognitive subscale, is useful for evaluating ATD patients, especially in the early phases of deterioration. It discriminates between ATD and CDND patients well.