Purpose: To investigate the effect of postextraction substrate aging on the microtensile bond strength (µTBS) of an adhesive system (Excite). Materials and Methods: Sixty sound human third molars were extracted for orthodontic purposes and prepared after the following storage periods in distilled water at 37°C (n = 10): G1 - 1 h; G2 - 24 h; G3 - 7 days; G4 - 30 days; G5 - 1 year; G6 - 2 years. The occlusal surfaces were removed using diamond disks to expose middle dentin and a standardized smear layer was created by polishing with wet 600-grit sandpaper. The adhesive system was applied according to the manufacturer's instructions, and a resin composite block (5 mm in height, Tetric Ceram shade A2/Ivoclar Vivadent) was built in 1-mm increments, each one being light cured for 40 s (600 mW/cm2). After storage in distilled water at 37°C for 24 h, teeth were sectioned to obtain stick-shaped specimens with a cross-sectional area of approximately 0.7 ± 0.2 mm2. Specimens were submitted to µTBS test in a Kratos universal testing machine at a crosshead speed of 0.5 mm/min. Data were statistically analyzed using one-way ANOVA at a significance level of 5% (p 0.05) Results: The mean µTBS in MPa ± SD were: G1 = 47 ± 3.1; G2 = 42 ± 5.1; G3 = 41 ± 6.4; G4 = 43 ± 9.8; G5 = 40 ± 7.0; G6 = 52 ± 5.7. No statistically significant difference was found among experimental groups. Conclusion: Human teeth stored for long periods of time can be used to determine the in vitro µTBS of one-bottle adhesive systems. Keywords: microtensile bond strength, dentin aging, adhesive systems