In 45 patients meeting NINCDS-ARDRA criteria for probably diagnosis of Alzheimer disease (AD), ApoE genotype and tau protein level in cerebro-spinal fluid (CSF) were determined. Frequency of e4 allele occurrence in group of AD patients was 73.3% and showed high statistic significance in comparison with control group. Increase of tau protein level in CSF was also statistically significant. No correlation in ApoE allele and tau protein level in CSF was revealed. The authors emphasize the usefulness of tau protein level measurement and determination of ApoE allele in diagnosis of Alzheimer disease.