Abstract: This study evaluated the effect of surface conditioning methods and adhesive systems on the repair bond strength of resin composites. Specimens (FLS: Filtek LS) (N = 144) were prepared using a silicone matrix. The specimens were stored in distilled water and then were randomly divided into the twelve groups (n = 12) according to the surface conditioning method (unground or diamond bur) and adhesive system (no adhesive, LS: Filtek LS, AS: Adper Scotchbond SE Plus) and resin composite (FLS: Filtek LS; FS: Filtek Supreme). The specimens were fixed in an hourglass-shaped silicone matrix and the other half of the specimen was restored. Hourglass-shaped specimens (n = 12) were used as positive control to measure the cohesive strength of the resin composite (Filtek LS). Microtensile bond test was performed (0.5 mm/min) and failure types were analyzed. Data were analyzed using two-way analysis of variance, Tukey's and Dunnett's tests (alpha = 0.05). Adhesive protocol and resin composite significantly affected the results (p < 0.05). For the FS composite, the highest results were obtained using LS adhesive with (18.4 +/- 7.7) and without (18.8 +/- 4.8) bur roughening. For FLS composite, the highest results were obtained using AS adhesive with (33.2 +/- 7.1) and without (25.7 +/- 3.6) bur roughening. Without the use of adhesive resin, significantly lower bond strength results were observed with both LS (5 +/- 2.1, 4.5 +/- 1.5) and FLS (2.2 +/- 1.2, 4.4 +/- 1.1) for unground and diamond bur roughened groups, respectively (p < 0.0001). Cohesive strength of the FLS (52.3 +/- 7.6) was significantly higher than any of the repaired groups (p < 0.0001). FS-LS combination and the groups repaired without adhesive presented more adhesive (Type I) failures Ver menos