Purpose:This study examined the influence of the adhesive strength between fiberreinforced composites (FRC) and veneering composites on the fracture load of combinations of these materials. Materials and Methods:Six materials were used. An experimental material called BR-100, Vectris, and FibreKor were the types of FRC. Estenia, Targis, and Sculpture were used as veneering composites. With the Estenia/BR-100 combination, the surface of the FRC was subjected to three different conditions before veneering. Ten specimens of each combination were fabricated and divided into two groups: One group was stored in 37°C distilled water for 24 hours, and the other was thermocycled (4°C/60°C, 10,000 cycles). Adhesive strength between FRCs and veneering composites was determined using the compressive shear strength test. In addition, fracture loads of laminate specimens were determined. Results:Good adhesive strength was obtained by leaving an unpolymerized layer on the surface of the FRC or by performing silane and bonding treatment. In the Estenia/BR-100 combination, when the adhesive strength was low, the fracture load of the laminate specimens was also low. However, the difference in fracture load was not as large as that seen in adhesive strength. The fracture load of each laminate specimen was significantly lower after thermocycling. Conclusion:The adhesive strength between the FRCs and veneering composite had an effect on the fracture load of the combination. Int J Prosthodont 2004;17:364–368.