Definitive diagnosis of Alzheimer's disease (AD) is made by pathologic examination of postmortem brain tissue in conjunction with a clinical history of dementia. To date, there are no good biological markers for a positive diagnosis of AD in the living patient. In an effort to identify biological markers useful both in the clinical and pathologic diagnosis of AD, we have investigated disease-specific protein alterations in cultured olfactory neurons. Olfactory neurons are readily accessible by biopsy, can be propagated in primary cell culture as olfactory neuroblasts (ONs), and exhibit several elements of AD brain pathophysiology making them powerful tools for the study of AD. Two-dimensional gel analysis of ON proteins from neuropsychologically evaluated AD donors revealed a set of five proteins (Mr 17-50 kD, pI 4.8-6.7) that were significantly altered in concentration when compared to cells from age-matched controls. Further characterization and microsequence analysis could lead to the identification of proteins that may have important diagnostic or therapeutic value in the treatment of AD.