A new corrosion inhibitor namely 4-amino-3-butyl-5-mercapto-1,2,4-triazole (ABMT) has been synthesized and its inhibitive performance towards the corrosion of mild steel in 1 N sulphuric acid (H2SO4) investigated by weight loss and potentiodynamic polarization techniques. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitor is of mixed type. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Temkin's adsorption isotherm. The influence of temperature, immersion time and acid concentration was also studied in the presence of ABMT in H2SO4. (C) 2002 Elsevier Science B.V. All rights reserved.