In this work, we explored the existence of genetic variant within the apolipoprotein E gene transcriptional regulatory region. Upon a population study, three polymorphic sites (-491, -427 and -219) and two mutations were found. We investigated newly reported -427T/C promoter polymorphism in association with sporadic Alzheimer's disease (AD), vascular (VD) and mixed dementia (MD) along with APOE genotype and gender. Observed polymorphisms were investigated in 267 subjects, 122 of them formed a control group, the group of patients consisted of 145 subjects. Sixty patients were diagnosed with AD, 41 patients were diagnosed with VD and 35 patients left were diagnosed with MD in Slovak Caucasians (Central Europe). Gene-gene interaction analysis showed increase of the risk to develop AD in subjects carrying both the at least one C allele and the APOE E4 allele (OR = 17.93, 95%CI = 3.50-171.54).