A continuing challenge in materials design is the achievement of high operational efficiency through improvements in performance criterion, particularly its service life-time characteristics. Benzotriazole (BTAH) has now been in use for many years for the protection of copper and copper alloys against various forms of corrosion. In this review, the chemistry of BTAH and theories regarding its mode of action are summarized. Also, a survey of the reported work in both clean and polluted environments is documented. More interestingly, the adverse effect of BTAH on the corrosion of Cu and Cu alloys in sulfide polluted environments is introduced.