Background: The formation of neuritic plaques with a β-amyloid peptide (βA4) core is a histopathological hallmark of Alzheimer's disease (AD). Proteolytic cleavage of the amyloid precursor protein (APP) may lead to overproduction of βA4. Genes involved in the proteolytic processing of APP are therefore candidates for AD. Mutations in the presenilin-1 (PS-1) gene lead to early-onset AD. An intronic polymorphism of the PS-1 gene is associated with late-onset AD. Cathepsin D (CD) is a lysosomal protein which leads to the accumulation of βA4 in vitro via proteolytic cleavage of APP. A recent report suggests that a missense polymorphism in the CD gene is associated with increased secretion of CD. The aim of the present study is to investigate the impact of the polymorphisms in the PS-1 and CD genes on AD. Method: Blood samples from 107 patients with AD and 102 age- and sex-matched healthy controls were collected and DNA was extracted. Genotyping of the intronic polymorphism in the PS-1 gene was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) as described previously. A new PCR-RFLP method was developed to detect the CD poly-morphism. Two primers were designed to amplify the CD pro-fragment region which includes the polymorphic region, a C → T transition at position 224. The resulting 349 bp fragment was digested with the restriction enzyme Mwo I and run on a 4% agarose gel. The bands were stained with GelStar®. Two different alleles (C, T) were distinguished as different band patterns. Allelic distribution was analyzed by χ2-test. Results and Conclusions: The data show that our method for the detection of the CD polymorphism is efficient and reliable. The most common CD genotype was C/C; T/T was rare in the present sample. This is the first report investigating the CD polymorphism with respect to AD. The association between PS-1 polymorphism and AD was weak, larger samples of elderly individuals are required to assess the role of the PS-1 polymorphism on late-onset AD.