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Objective. To evaluate the adequacy of fluoride levels in the public water system in Curitiba, state of Parana, Brazil, as determined by two techniques (colorimetric and electrometric). Methods. Data from independent measurements of fluoride in the public water system in Curitiba routinely performed by the city government were obtained for the period between January 2000 and July 2008. Mean levels of fluoride concentration were calculated for each of these years. After that, fluoride concentrations measured in 1 470 samples by the state water utility (SANEPAR) using the electrometric technique in 2006 and 2007 were compared with the corresponding levels measured by the city using the colorimetric method. The rate of samples meeting the standard for the city (0.8 ppmF), and below and above the standard, was calculated for both methods. Fluoride levels were compared between sanitary districts, months for the period between December 2007 and July 2008, and water treatment facilities. Results. The overall mean fluoride level between 2000 and 2008 was 0.7 ppmF based on the independent measurements. The comparison between techniques showed a higher mean fluoride level with the electrometric technique (0.743 ppmF ± 0.133) vs. the colorimetric technique (0.637 ppmF ± 0.164). The rate of samples meeting the ideal standard of 0.8 ppmF was 15.05% for the colorimetric and 63.97% for the electrometric technique; 62.03% and 22.85% of the samples were below that standard and 21.10% and 13.18% were above that standard, respectively. Fluoride levels were statistically significant (P ≤ 0.001) for the comparison between sanitary districts and months. Conclusions. The choice of technique significantly influences the resulting levels of fluoride. Independent monitoring of fluoride levels should employ the same technique used by the water utility. Further studies should aim at defining which technique is the most adequate to determine fluoride concentration in public water systems. [ABSTRACT FROM AUTHOR]