The influence of aminophenols on the corrosion and hydrogen permeation of mild steel in 1 M HCl and 0.5 M H2SO4 has been studied using weight loss and gasometric measurements and various electrochemical techniques. All the isomers of aminophenol inhibit the corrosion of mild steel in 1 M HCl and accelerate it in 0.5 M H2SO4. They behave predominantly as cathodic inhibitors. Aminophenols, except PAP in 1 M HCl, enhance the permeation current in both the acids. The adsorption of PAP on the mild steel surface in 1 M HCl obeys the Langmuir adsorption isotherm. Surface analysis and ultraviolet spectral studies are also carried out to establish the mechanism of corrosion inhibition and acceleration of mild steel in acidic solutions.