Benzotriazole (BTAH) affects the localized corrosion of Cu10Ni alloy in 3.4% NaCl salt water containing 2 ppm sulfide ions. BTAH concentrations > 5 x 10-4 M imparted corrosion inhibiting efficiency that increased with its concentration. On the other hand, a concentration of 10-4 M BTAH acted as a promoter of pitting corrosion of the alloy in the above medium. The results of optical and scanning electron microscopy could be rationalized on the basis of competitive adsorption of BTAH and sulfide ions on the alloy surface and the formation of copper oxide and copper sulfide. The presence of the above phases was identified in the xray diffraction spectra of the corrosion products.