ABSTRACTThis study assessed the roles of Tau gene short tandem repeats (STRs) nested within intron 1 (rs5820604 and rs10675722) and Apolipoprotein E (ApoE) gene polymorphisms in 70 late-onset Alzheimer's disease (AD) subjects, 70 vascular dementia (VD) subjects, and 70 normal controls (NCs) in Guizhou Han population. Our data suggest that the Tau gene STR loci rs5820604 (CA)19 allele may increase the risk of AD, whereas the (CA)16 allele may be protective. The Tau gene STR loci rs10675722 (TA)17 allele may increase the risk for AD and VD. In addition, a synergistic effect of polymorphisms in ApoE ε4 and Tau gene STR loci rs5820604 (CA)19 allele was found in the pathogenesis of AD (p = .025, OR [odds ratio] = 3.178, 95% CI [confidence interval] = 1.156–8.741).