Purpose: The aim of this preliminary in vitro study was to evaluate the effect of a casein phosphopeptide and amorphous calcium phosphate (CPP-ACP) paste on untreated enamel surfaces that had previously been exposed to an erosive challenge. Materials and Methods: Over a period of 6 h, enamel samples from five fully erupted, caries-free molars were incubated with apple juice and later covered with CPP-ACP paste for 15 min. Enamel samples incubated with physiological sodium chloride solution or with apple juice alone served as controls. The quantitative elementary analysis for calcium and phosphorus in various depths ranging from 5 to 50 lm was performed using an electron-probe microanalyser. Results: Exposure to apple juice resulted in a loss of minerals down to a depth of 30 lm with a mean loss of 13% at 5 lm and 6% at 10 lm. After treatment with CPP-ACP paste, the mineral loss decreased to a mean of 9% at 5 lm and remained at 5% at a depth of 10 lm (not a statistically significant difference). At a depth of 20 lm, no further mineral loss was recorded. Conclusions: This study demonstrated that there is a slight gain in the mineral contents after the application of a CPP-ACP paste, mainly in the upper enamel layer. Within the limitations of this in vitro study, the application of CPP-ACP paste may enhance the remineralisation after an erosive challenge and thus offer some protection for patients who are at risk for erosion. Schlagwörter: casein phosphopeptide and amorphous calcium phosphate, electron-probe microanalysis, enamel erosion, in vitro study, remineralisation