Recent studies have reported a genetic association between the 73 G/A polymorphism within exon 1 of the cystatin C gene and Alzheimer's disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of CST3 as risk factor for AD, we analyzed the genotype and allele frequency distribution of CST3 G73A and apolipoprotein (ApoE) gene polymorphisms in 243 Italian patients with AD and 186 controls. Patients with AD were consecutively collected among the outpatients from the Neurology Department at the University of Florence. All 429 subjects were genotyped for CST3 and ApoE polymorphisms. After stratification according to age, the GG frequency resulted slightly higher in younger (<65 years) cases, but far from statistically significant. There was also no evidence of a statistical interaction between CST3 and ApoE polymorphisms. In conclusion, our data suggest that the CST3 genetic variant is not a susceptibility factor in AD, nor mitigate the effect of the ApoE varepsilon4 allele in the risk of developing AD.