Current dental diagnostic methods can detect caries but cannot quantify the mineral status of a lesion. Quantitative lightinduced fluorescence (QLF) measures the percentage of fluorescence change of demineralized enamel with respect to surrounding sound enamel, and relates it directly to the amount of mineral lost during demineralization. Development of caries-like lesions and subsequent remineralization of the lesions were monitored by QLF. The results showed that the percentage of fluorescence change (?Q) increased linearly with the demineralization time and decreased with increased remineralization time. Stained teeth were whitened with a bleaching agent and the change in stain intensity (?E ) was quantified using QLF. The results showed that ?E decreased linearly as the tooth regained its natural color. Factors that might affect the use of QLF to detect and quantify caries were also examined. It was concluded that QLF could be used to detect and longitudinally monitor the progression or remineralization of incipient caries, however lesion detection may be limited by the presence of saliva or plaque and enhanced by staining. The change in shade of discolored teeth by whitening agents could be quantitatively measured by QLF.