Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Objective: To evaluate the effect of fluoride (F) varnishes supplemented or not with sodium trimetaphosphate (TMP) on enamel erosive wear followed or not by abrasion in situ.Methods: Ten volunteers were selected and randomly divided into four groups, according to the varnishes tested: placebo (no F or TMP), 5% NaF (positive control), 2.5% NaF and 2.5% NaF/5% TMP. Enamel blocks (n = 4) were mounted in palatal devices and received an application of each test varnish, following a double-blind, crossover protocol. After 6 h, varnishes were completely removed and the blocks were subjected to erosive challenges by ex vivo immersion in citric acid (5 min, 4x/dia, 5 days). Following, half of the blocks were subjected to abrasion by brushing with a placebo dentifrice slurry for 15 s. Enamel wear (mu m), surface hardness (SHf) and cross-sectional hardness (Delta KHN) were assessed after each experimental period.Results were analyzed by ANOVA, Student-Newman-Keuls's test and Pearson correlation coefficient (p