The widespread use of antioxidants in the food processing industries, especially oil and oil based ones, has great economic advantages. Yet since the ban on the further usage of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) by the FAO in 1980, there have been several reports indicating that BHA and BHT might have both beneficial and detrimental effects. Studies were performed in healthy mature rats both males and females in a 1:1 ratio. In vitro estimations of the percentage hemolysis (50% hemolysis indicating a 50% toxicity level) showed that BHT is more toxic than BHA and the hemolytic activities (kinetics) showed a peak at 60-65% after 12 min with BHT and at 50% after 20 min with BHA. This clearly indicates that at the concentrations of 0.75%, BHA and BHT are harmful to the blood. Further work of dietary effects on blood is in progress. Thus while BHA and BHT are known to be metabolized in the liver and eliminated through the urine, they might be very detrimental to the circulatory system.