Since the loss of cholinergic neurons in the Alzheimer's disease (AD) brain was first reported, considerable evidence in vivo and in vitro has accumulated in support of the cholinergic hypothesis of AD. The hypothesis is greatly supported by the fact that the most promising drugs against AD are inhibitors of acetylcholinesterase (AChE). To identify the possible mutations and/or polymorphisms of neuronal nicotinic acetylcholine receptor (nAChR) genes related to the pathogenesis of sporadic AD, we have performed mutational analyses of the major neuronal nAChR genes (CHRNA3, 4, 7 and CHRNB2) expressed in central nervous system. Allelic analysis showed association of specific silent or intronic polymorphisms of the CHRNA3 and CHRNA4 genes and AD. Two novel missense point mutations, Ser413Leu in the CHRNA4 gene and Gln397Pro in the CHRNB2 gene, were identified in two different AD cases but were not found in other AD cases and controls. These findings suggested that genetic polymorphisms of the neuronal nAChR genes might be related to the pathogenesis of sporadic AD.