The effect of inorganic acid fumes from the work environment on the erosion of teeth was studied blindly. A sample of 186 workers was drawn from four factories. Among the 157 dentulous participants, 76 were working in departments containing acid fumes, and 81 had never worked under such conditions and were used as referents. Of the acid workers 18.4% had one or more teeth with erosion, and the corresponding figure for the referents was 8.6%. With a longer duration of exposure the proportion of subjects with erosion increased. The acid workers had more teeth with erosion than the referents, especially upper anterior teeth. The findings suggest that even today exposure to inorganic acid fumes from the work environment may increase the erosion of teeth, especially the upper anterior teeth, which are not continuously protected by saliva and the lips.