AIM: To investigate the possible association of hereditary polymorphism of N-acetyltransferase 2 (NAT2) gene with the susceptibility towards senile dementia in fanner population of Shanghai suburb. METHODS: NAT2 gene genotyping was performed at 7 major polymorphic loci (G(191)A, C(282)T, T(341)C, C(481)T, G(590)A, A(803)G, and G(857)A) with a polymerase chain reaction-based restriction fragment length polymorphism based procedure in 2 groups of farmer subjects in Shanghai suburb. A group of 51 diagnosed dementia patients [comprising 29 sporadic Alzheimer disease (AD) patients and 22 sporadic vascular dementia (VD) patients] and a group of 112 healthy individuals were in the same area. RESULTS: The homogenous rapid genotypes (R/R, including *4/*4, *13/*13, and *4/*13) was found over-present in both groups of patients, compared with healthy individuals, for all farmer dementia patients, 52.9% vs 33.0%, P=0.016, OR (95% Cl): 2.28(l.16-4.48); for AD group only, 51.7% vs 33.0%, P=0.063, OR (95% Cl): 2.18 (0.95-4.97); for VD group 54.5% vs 33.0%, P=0.055, OR (95% Cl): 2.43 (0.96-2.43). The significant frequency difference of genotype *4/*7B between farmer dementia patients and healthy individuals, and that of solo-alleles *13, and *7B were observed between the healthy individuals and both groups of dementia patients. CONCLUSION: Our data suggest the involvement of various NAT2 rapid-acetylating genotypes in the individual susceptibility to senile dementia. Variant genotypes of NAT2 might serve as a hereditary risk factor for AD and VD in Chinese population.