Butylated hydroxytoluene (BHT) and sodium nitrate (SN) are widely used as food additives. The experimental evidence on carcinogenicity and the limitation of data on the aneugenic effects of BHT and SN triggered us to study their effect on cellular proliferation mechanism and aneuploidy status. The proliferative and aneugenic effects of BHT and SN were tested on the Feulgen-stained Tetrahymena pyriformis macronuclei using computerized DNA image analysis. For this purpose, the acutely non-toxic (for both food additives) dose of 0.2 M was administered for 24 hours to protozoa cultures following DNA image analysis of T. pyriformis nuclei. The analysis was based on the measurement of the following parameters associated with macronuclear proliferation and aneuploidy status: Proliferation Index (PI), Ploidy Balance (PB) and Degree of Aneuploidy (DA). The results have shown that both BHT and SN, at the experimental conditions tested, induce independently an increase in the proliferation (expressed as an increase in the PI) and aneuploidy (expressed as a decrease in PB and an increase in DA) of 24 hours exposed T. pyriformis macronuclei, with SN possessing a more potent aneugenic effect compared to BHT. These findings exhibit the proliferative and aneugenic profile of BHT and SN and complement previous findings on their correlation with adverse toxicological effects and carcinogenesis.