An adequate repair procedure depends on high bond strength between the existing composite and the new composite. To evaluate the effect of surface treatments and bonding procedures on the bond strength of repairs performed 24 hours after composite polymerization. Composite specimens were stored in distilled water at 37 degrees C for 24 hours. Specimens were allocated into 12 groups (N=10) according to the combination of surface treatment (none, air abrasion, diamond bur) and bonding procedure (none, Single Bond after H(3)PO(4) cleansing, Clearfil SE Bond after H(3)PO(4) cleansing, Clearfil SE Bond without H(3)PO(4) cleansing). The ultimate tensile strength (UTS) of the composite was tested in nonrepaired specimens. Twenty-four hours after repair, specimens were sectioned into three slabs and trimmed to an hourglass shape (1 mm(2) area). Slabs were tested under tension and mean bond strengths analyzed with two-way analysis of variance/Tukey and Dunnett tests (alpha=5%). Two groups resulted in repair bond strengths similar to composite UTS: air abrasion combined with Clearfil SE Bond after H(3)PO(4) cleansing, and air abrasion combined with Clearfil SE Bond without H(3)PO(4) cleansing. Combinations of surface treatments and bonding procedures were not statistically different. When repair procedure was performed 24 hours after composite polymerization, different combinations of surface treatments and bonding procedures affected repair bond strength similarly. There was no statistical difference between the repair bond strength of groups air-abraded and bonded with the self-etching system and composite UTS. Only air abrasion associated with a self-etching system provided repair bond strength comparable to composite UTS.1990-8; discussion 99