Objectives: This study aimed to evaluate enamel surface roughness (Ra) after etching with a self-etching primer and/or H₃PO₄, the micro-tensile bond strength (µTBS) of two bonding agents (Single Bond, SB and Clearfil SE Bond, CF) applied over treated enamel surfaces, and the correlation between Ra and µTBS. Methods: Enamel blocks were polished with abrasive papers and diamond pastes. Initial Ra was analyzed and enamel was etched according to the following experimental groups (n=5): I- 35% H₃PO₄ for 15s; II- 35% H₃PO₄ for 60s; III- CF primer for 20s; IV- CF primer for 60s; V- H₃PO₄ for 15s + CF primer for 20s. A new measurement of Ra was performed, and enamel surfaces were bonded with either SB (groups I and II) or CF (III, IV and V). Afterwards, a composite build-up was constructed on enamel surfaces, and specimens were vertically, serially sectioned into 0.8mm thick slabs, which had their cross-sectional area reduced to approximately 0.8mm². Specimens were tested in the microtensile mode at a crosshead speed of 0.5mm/min. Ra values were submitted to repeated measures ANOVA and Tukey test, which detected significant differences between initial and final Ra values for all tested groups. Results: Groups III and IV presented significantly inferior Ra values. The highest µTBS means were observed for groups I (29.78±3.85^a) and V (28.11±5.82^a), which were significantly higher than II (20.25±3.40^b) and III (20.24±2.83^b). Group IV (26.50±1.66^ab) presented intermediate µTBS values. A significant positive correlation was observed between Ra and µTBS. Conclusion: Etching enamel polished surfaces with H₃PO₄ resulted in higher µTBS values, independently of the application time. This study was supported by FAPESP#01/13034-3 and CAPES

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