Objectives: To compare two surveys across seven states for the prevalence of dental caries among Mexican schoolchildren. Study D esign: Analysis of two cross-sectional surveys: Schoolchildren from 6 to 10 years of age were examined in the 1988?1989 survey and 6- to 10-year-old and 12-year-old students were included in the 1998?2001 survey. The baseline data of seven states were available for analysis. Representative probability samples were conducted statewide in both surveys. The World Health Organization (WHO) method was used to obtain the dental caries index (dmft, DMFT). At present, additional and more recent epidemiological data representative statewide in Mexico are unavailable. Results: The participants were 9798 schoolchildren in the 1988?1989 survey and 16882 schoolchildren in the 1998?2001 survey. The prevalence of caries in children ages 6 to 10 years was 86,6% in the first survey and 65,5% in the second survey, showing a 24,4% reduction. The primary teeth index in the first survey was dmft = 3,86 (IC95% 3,68 4,04) and in permanent teeth, it was DMFT = 1,03 (IC95% 0,95 1,11). In the second survey, the comparable values were dmft = 2,36 (IC95% 2,20 2,52) and DMFT = 0,35 (IC95% 0,29 0,40), corresponding to a reduction of 38,89% and 66,02% in the primary and permanent dentition, respectively. Treatment needs remain high: In the second survey, as 92,75% of the index DMFT was conformed as decayed teeth. Conclusion: Overall, we detected a downward trend in the dental caries indices, particularly in the permanent dentition. The increase in the availability of fluoride likely contributed to the observed decline in dental caries