The fear of Alzheimer's disease for both patients and families is growing along with the increasing evidence of the disease itself. This study (N = 312) of the validity of the clock drawing test in screening patients with probable Alzheimer's disease was conducted in an active outpatient geriatric clinic. Clock drawings by patients with normal mental status or depression were essentially normal. Alzheimer's patients were unable to complete a normal clock and demonstrated five characteristically abnormal patterns. As a test for Alzheimer's disease, clock drawing had a sensitivity of 86.7% and a specificity of 92.7%. There was correct identification in 97.2% of normals. These findings indicate that the clock drawing test, an easily administered, low cost screening tool, can be useful to health care professionals in characterizing cognitive loss in a general geriatric clinic population.