The influence of anions such as chloride and sulphate on the inhibition of corrosion of mild steel by p-tolyl thiourea (PTTU) in 1N HCl and 1N H2SO4 has been studied using weight loss and gasometric measurements, galvanostatic polarisation studies and ac impedance measurements. The compound is found to be less inhibitive in 1N HCl than in 1N H2SO4. The influence of p-tolyl thiourea on the extent of hydrogen permeated through mild steel in acidic solutions has been studied using electro-permeation technique. The compound is found to enhance the permeation of hydrogen through mild steel in both the acids. The adsorption of p-tolyl thiourea on the mild steel surface from both the acids obeys Temkin's adsorption isotherm. The increase of charge transfer resistance (R-t) and decrease in double layer capacitance (C-dl) values of the metal electrode in the presence of the test compound (PTTU) show the adsorption of the compound on the metal surface.