High fructose corn syrup is the favorable sweetener for food and beverage production because of its advantages over table sugar in some applications. Previous studies showed that it causes metabolic disorders and obesity. In this study, the genotoxic effect of HFCS was investigated using the A. cepa root tips as a genetic model. Five concentrations, 2 mL/L, 1 mL/L, 0.5 mL/L, 0.25 mL/L, 0.125 mL/L, were employed. Because the highest two concentrations greatly inhibited mitosis they were excluded. Results of the other three concentrations showed inhibition of mitosis. This was reflected by decreasing of the mitotic index with increasing HFCS concentration. Also, increasing of HFCS concentration increased the number of prophase cells compared to the other three mitotic stages indicating that HFCS inhibited the progression from prophase to metaphase stage. Different types of chromosomal aberrations were detected including stickiness, vagrant and lagging chromosomes, bridge, disturbed metaphase, pole to pole metaphase. These types of chromosomal aberrations increased with increasing of the concentration of HFCS.