Neprilysin (NEP), also known as neutral endopeptidase, enkephalinase, CD 10, and common acute lymphoblastic leukemia antigen, is a 97-kD protein. NEP can degrade amyloid β peptides, and its mRNA and protein levels are known to be reduced in the brains of patients with Alzheimer’s disease (AD), making the <i>NEP</i> gene a substantial candidate for an AD risk factor. We examined the genetic association of three <i>NEP</i> polymorphisms, a GT-repeat polymorphism and two single nucleotide polymorphisms (SNPs, –1075A>G and –1284G>C) in its promoter region, with AD in a Japanese case-control sample (240 patients and 163 controls). The GT-repeat polymorphism, but not the SNPs, was significantly associated with late-onset AD (p = 0.0007). Our findings suggest that the GT-repeat polymorphism in the promoter region of the <i>NEP</i> gene or some other unknown polymorphisms, which are in a linkage disequilibrium, confer a susceptibility to late-onset AD.