The authors report the clinical findings and the results of molecular genetic analysis of 8 patients with sporadic Alzheimer's disease. Differential diagnosis was carried out on the basis of familial history, laboratory data, brain imaging analysis using CT, MRI and SPECT. According to the clinical stage criteria made by Cummings and Benson, 6 cases were in stage 1 and the remaining 2 in stage 2. Recently, it was reported that affected members from 6 Japanese kindreds with familial Alzheimer's disease (FAD) had missense mutation in exon 17 of the gene for beta/A4 amyloid precursor protein (APP). Amino acid substitution (Val-Ile) at codon 717 by this mutation was considered to be responsible for FAD in these kindreds. We used genomic DNA from 8 sporadic cases to determine whether the disease in these families is associated with an APP 717 mutation and the mutated codons, 102, 117, 129, 178, and 200, on the gene for proteinase-resistant prion protein (Prp) which causes transmissible dementia, Creuzfelt-Jacob disease (CJD) and Gerstmann-Sträussler syndrome (GSS). The results showed that there were no mutations on these genes in 8 patients. It would be necessary to analyze DNA from patient with sporadic Alzheimer's disease to examine the mutations found in the APP gene and Prp gene of heredity Alzheimer's disease patients.