AbstractThe purpose of this study was to evaluate the preeruptive effect of NaF tablets on caries in proximal surfaces of permanent molars and premolars. The material consisted of 47 subjects who had consumed fluoride tablets for a minimum of 5 yr between 1/2 and 6 yr of age in accordance with recommendations from the National Swedish Board of Health and Welfare (F+‐group) and 69 comparable children who had never consumed such tablets (F‐‐group). All had resided since birth in an area with a water fluoride concentration of 0.2 ppm and had been exposed to fluorides in toothpaste, mouthrinse solution and varnish since at least the age of 6. The children were examined by means of bitewing radiographs at the ages of 12, 13, 14 and 17. Two confounding factors, i.e. salivary counts of Streptococcus mutans and lactobacilli, were estimated and used for correction of crude caries differences. The mean values of these factors were higher in the F‐‐group than in the F+‐group. The results showed a statistically significantly higher caries prevalence in the F‐‐group compared to the F+‐group when the children were 14‐yr‐old, 4.4 vs. 2.9 DFS, corresponding to a caries reduction of about 34%. After correction for confounding, this was reduced to 24%, representing a non‐significant difference of 1.1 DFS but still indicating a preemptive effect. At the age of 17, the difference in caries prevalence was statistically not significant, 7.1 vs. 5.6 DFS, corresponding to a reduction of 21%. Based on corrected data, this was reduced to 15%. A main finding was that caries reducti