Diffusion across the enamel is the underlying principle of many physiological, pathological and clinical processes of enamel. Even though enamel diffusion is intrinsically related to several important events, it remains as a mysterious phenomenon with plethora of confusing qualitative data and descriptions. On the other hand, FRAP (Fluorescence Recovery After Photobleaching) with the advent of CLSM (Confocal Laser Scanning Microscope) has become a standard tool for measuring effective diffusion coefficients in many biological tissues. Objectives: Our objectives are to measure enamel diffusion coefficients quantitatively and to evaluate the feasibility of FRAP for dental hard tissue research. Methods: Nine caries free molar were microtomed into 200±10µm thick sections, characterized morphologically and guided histologically by Stereomicroscope and Polarized Light Microscope in conducting FRAP. The enamel sections were incubated in Fluorescein 200nM 0.8ml in paraffin-sealed chambers at 23ºC overnight and diffusion coefficients of enamel were measured 10 times each spot by FRAP under CLSM. The diffusion coefficient, mobile fraction and bleaching parameter were retrieved by nonlinear regression curve fitting using self-written code in Mathematica 5. Results: The mean diffusion coefficient measured with FRAP under CLSM was calculated to be 1.93x10-7cm2/s (SD 2.97x10-8) and was in consistent with previously documented range (documented range 10-7-10-11cm2/s). Conclusion: This pilot study has identified FRAP combined with CLSM to be a promising technique for investigating human enamel micro-diffusion quantitatively and the results obtained with Fluorescein dye appeared to be consistent, reproducible and reliable. (This study was supported by BMRC Grant R-222-000-015-305).