Despite a significant increase in the amount of research being conducted on the etiology, diagnosis, and treatment of Alzheimer's disease and other dementing disorders, there has been little assessment of the utilization of this new wealth of information by the primary care physician. It was hypothesized that there would be a wide variation in physicians' knowledge of dementing disorders and the procedures used to diagnose these disorders. To quantitate the present status of primary care physicians' knowledge of dementing disorders and to investigate possible relationships between this knowledge and different physician and practice characteristics, 50 general internists and family practitioners from Winnebago County, Illinois, were interviewed regarding their recall of causes of dementia, procedures used in diagnosing these diseases, treatment recommendations, and comfort in making a differential diagnosis. Results revealed a wide variation in both physicians' familiarity with the causes of dementia as well as the procedures used in making the diagnosis. Although a majority (80%) of the physicians reported some degree of confidence in making a differential diagnosis of dementing disorders, a significant trend was found between physician age and comfort in making the diagnosis, with age being directly correlated with comfort. This was in spite of a significant negative association between physician age and immediate recall of causes of dementia. These data imply that younger physicians are entering the work force with at least better immediate recall of information on dementing disorders, but they have had little opportunity to become comfortable with that knowledge due to a generally smaller geriatric population in their practice.(ABSTRACT TRUNCATED AT 250 WORDS)