Abstract: More than hundred million people from almost 25 countries, including India, were affected by fluorosis. Thus the objective of the study was to study the prevalence of dental fluorosis in high fluoride areas around Lucknow and to evaluate the role of calcium in dental fluorosis. Water survey from different areas was done to identify high fluoride area in Unnao district of Uttar Pradesh, India. House to house survey of more than 5000 population was done. Biochemical tests were performed in 50 dental fluorotic and 50 non fluorotic randomized subjects. Clinical and biochemical status was recorded after 6 months of calcium supplementation. SPSS was used for statistical analysis. It was showed that 28.64% population had dental fluorosis (total fluorosis: 43%), highest in 13-15 years age group. After 6 months of calcium supplementation, 44% of cases showed reversal of dental fluorosis, whereas, in 40% of them disease did not progress further. Increase in serum calcium and significant decrease in urinary fluoride was observed post supplementation. This first large scale prospective community study, concluded that long term administration of calcium can reverse dental fluorosis especially in children with early grades of fluorosis.