Dementia is an acquired impairment of intellectual and memory functioning. There are numerous factors affecting neurocognitive functions like vascular factors, Vitamin B 12 and folate and homocysteine levels. The aim of this study is to determine whether there is a relationship between the serum levels of these metabolites and diagnosis of dementia and mild cognitive impairment (MCI). A total of 1249 patients admitted to Hacettepe University Hospital Department of Internal Medicine, Division of Geriatric Medicine Outpatient Clinic between I February 2002 and 30 June 2003 were included in this study. Vitamin B 12, folate and homocysteine levels were measured in all patients, and they were evaluated also for their cognitive abilities. In this study pool, 121 cases were diagnosed as Alzheimer's disease (AD), 60 patients were diagnosed as having non-Alzheimer dementia (NAD), 273 had MCI. When patients with AD, NAD, MCI and patients without dementia were compared according to their median values of folate, Vitamin B 12 and homocysteine, there were no significant differences. Results of studies searching for a correlation between Vitamin B-12, folate and homocysteine levels and their relation with cognitive status of the elderly are controversial in various studies from different countries. In this study (with 1249 elderly patients) we were unable to find any correlation between homocysteine, Vitamin B12 and folate levels and cognitive functioning in contrast with some literary data. Nevertheless, these metabolites should be measured routinely in the examination of any elderly patient, since they can play important roles in geriatric patients. (C) 2004 Elsevier Ireland Ltd. All rights reserved.