The aim of this work is to assess the evolution of caries and fluorosis prevalence and indices at 7 and 12 years of age in the Canary Islands through three cross epidemiological studies conducted in 1991, 1998 and 2006. The three studies followed a similar methodology, using the WHO diagnosis criteria and indications, except for the assessment of fluorosis, which was measured with the ?Thylstrup and Fejerskov? index. The examining dentists were trained and calibrated in an area with high endemic fluorosis. The three studies took a sample of 1000 students for each age group. At 7 years of age, the decayed, and filled teeth (dft) varied from 1.42 in 1991 to 1.14 in 1998 and 1.37 in 2006. At 12 years of age, the Decayed, Missing, and Filled Teeth (DMFT) went from 1.86 to 1.21 and 1.51 in the three studies respectively and the significant caries index (SiC) went from 4.28 to 3.15 and 3.72. At this age, the Filled Rate rose from 24.05% in 1991 to 30.43% in 1998 and to 37.20% in 2006. In relation to fluorosis, at 12 years of age the percentage of healthy or fluorosis-free schoolchildren in the Canary Islands between the first and the second studies went down from 73% to 61.3% and went up to 78.5% in 2006, with a noticeable fall in the prevalence of children with severe and moderate fluorosis. Despite the fluctuations of caries shown in the three studies, at 12 years of age the Canary Islands have remained in the low level of caries of the WHO classification from 1991 up to now. The evolution in the prevalence of dental fluorosis shows the effect of the measures taken, 10 years after they were started.