Introduction: In this study we examined the effect of different concentration of Cycloheximide on the enhancement of Vero cell sensitivity to Vero cytotoxin (VT) of Escherichia coli. Materials and Method: Cycloheximide at different concentrations (0.5-16mg/ml) were added to vero cells, for different peroids of time: 1 day before, immediately after, or 1 and 2 days after the adddition of VT. Results: The additon of cycloheximide of 4 to 8 g/ml led to marked enhancement of VT titer. Cycloheximide-treated Vero cells were about eight times more sensitive to VT than normal cells. This effect being most demonstrated when the cycloheximide was added before the addition of toxin. It was showned that the effect was specific and cycloheximide (4 to 8 g/ml) alone has no effect on vero cells. Conclusion: The addition of cycloheximide increased the sensitivity of vero cell to Verotoxin without affecting the specificity of the assays.