The acid resistance of TiF4-treated enamel was investigated to establish a possible treatment modality for endogenous dental erosion. Enamel slabs were prepared from human molars and treated with solutions of TiF4. Scanning electron microscopy (SEM) and microhardness testing were used to examine the effects of the exposure of the treated enamel to strong acid. SEM micrographs showed the presence of heavy deposits on enamel surfaces. The surface coating, formed following TiF4 application, appeared to be resistant to severe acid attacks. Microhardness measurements showed that TiF4 treatment inhibited enamel softening. It is concluded that topical TiF4 application may be effective in prevention of dental erosion caused by hydrochloric acid from the stomach in patients with frequent vomiting or gastroesophageal reflux.