The aim of this study was to develop a titanium tetrafluoride (TiF₄) varnish and evaluate the stability of the formulation and its reactivity with dental enamel. The varnish was prepared in a resinous matrix using ethanol 96% as solvent. Samples (n=45) were aged at 65 °C and 30% of relativity humidity (RE n° 01/05—ANVISA) and after 3, 6, 9 and 12 months, nine samples were removed for evaluation and compared with fresh samples. Chemical stability of TiF₄ varnish was determinate by ¹⁹F-NMR and the reactivity of the formulation was quantified by formation of fluoride loosely (CaF₂) and firmly bound (fluorapatite; FA) to enamel. For reactivity comparisons, a varnish without TiF₄ was used as control. The loss of soluble fluoride was about 0.9% after one year of storage. The values of the reactivity (mean±S.D.) of fresh, aged at 3, 6, 9 and 12 months and control samples were: CaF₂ (μg F/mm²): 89.3±27.5^a; 54.5±14.3^b; 51.2±29.8^b; 69.3±21.3^a; 48.0±27.4^b; 0.10±0.07^c, FA (μg F/g): 2477.5±1044.0^a; 2484.8±992.0^a; 2580.0±1383.9^a; 2517.2±929.9^a; 2121.0±1059.2^a; 330.0±180.0^b, respectively. Means followed by distinct letters were statistically different (p<0.05). After one year of storage, the formulation was chemically stable and the levels of FA were maintained. However there was an initial decrease in the ability to form CaF₂.