The effect of a new green corrosion inhibitor,namely carboxymenthylchitosan(CM-chitosan),on the corrosion of mild steel in 1 mol·L-1 HCl and 0.5 mol·L-1 H2SO4 was investigated by various corrosion monitoring techniques.The results obtained revealed that this compound was a very good inhibitor and behaved better in 1 mol·L-1 HCl than 0.5 mol·L-1 H2SO4.In both 1 mol·L-1 HCl and 0.5 mol·L-1 H2SO4 solutions,the adsorption of CM-chitosan on the mild steel surface in both acidic media followed a modified Langmuir adsorption isotherm.