Acid erosion is the chemical effect of dietary or gastric acids on enamel and dentine. Unlike dental caries, which is a bacterially mediated condition, acid erosion normally is combined with physical forms of attrition and abrasion. The clinical appearance of acid erosion in the early stages is seen characteristically as hollowed-out lesions on occlusal surfaces and on smooth surfaces as a subtle change in the tooth contour. As the condition progresses, the lesions coalesce and form widespread dentin exposure and coronal destruction. Dietary acids that are present in beverages and fruits potentially can cause acid erosion. However, dietary habits involving frequent consumption of acids are believed to be important determinants in the risk of developing clinical signs of acid erosion. Prevention using fluoride toothpastes, dietary modifications, and calcium-based products probably have a significant clinical effect in reducing the risk of developing acid erosion.