The fluoride content in ready-to-drink 100 % fruit juice has been reported but the variation of the fluoride level has not been known.This experiment was done to investigate the fluoride level of the same type of fruit juice and companies in the two year. Objective: The objective of this study was to compare the fluoride content of pupolar ready-to-drink 100% fruit juice in the year 2001 and 2002 and the stability of fluoride content after 6 months storage. Methods: Twelve types of ready-to-drink 100% fruit juices were used. Fluoride analysis was performed using direct measurement with fluoride electrode (Orion model 96-04, 96-09) connected to Ion Analyser (Orion model 940, Orion, USA). Results: The fluoride ion concentration in fruit juices in the year 2001 and 2002 varied greatly among different fruit juices and different companies. The highest fluoride content was found in red grape juices in both years with the concentration of 1.064±0.007ppm and 0.649±0.060ppm, respectively. The lowest fluoride ion concentration in the year 2001 was found in guava juice (0.019±0.002ppm) while the lowest fluoride concentration in the year 2002 was found in mandarin juice (0.063±0.006ppm). The fluoride content was stable in 100% fruit juice during the period of 6 months storage. Conclusions: It was concluded that there were variations in the fluoride content in the popular ready-to-drink fruit juices sold in Bangkok. This may due to the nature of fruit, variation in insecticide used and different area of plantation. Supported by the Faculty of Dentistry, Mahidol University.