In this paper, the demineralization of dental enamel was studied in under-saturated calcium phosphate solutions with different pH and fluoride concentrations. The combined data of the mineral dissolved show a dissolution pattern not significantly different from the stoichiometric hydroxyapatite (HAP) dissolution [Ca/P = 1.72 (0.01)]. However, during the very initial demineralization, calcium is removed preferentially. The rate of demineralization seems to be affected to a greater extent when the solution is supersaturated to CaF2 than to fluorapatite (FAP). This is attributed to a different morphology of the calcium fluoride deposition which effectively blocks the acid diffusion. During demineralization, fluoride is taken up by the enamel; the percentage of fluoride being removed from the solution is correlated with the amount of demineralization.