Statement of Problem: Ceramic materials with excellent biocompatibility are widely used to achieve highly esthetic ceramic restorations. Although these ceramic materials usually provide an excellent restorations but failures do occur, and it is a challenge to the dentist. A number of composite resin systems are marketed for repair of failed porcelain restorations. Repair of failed porcelain restorations typically involves adhesion of a composite resin to the fractured porcelain. The porcelain surface can by physically altered with air abrasion, a diamond bur, or hydrofluoric acid (HF). Silanization of porcelain and viscosity of bonding agent is an important factor in this respect.Purpose: The goal of this study is to compare three commercially available composite resin materials and one type of porcelain, in relation to their bond strength under a flexural load with an instron testing machine.Materials and Methods: Fifty porcelain blocks of 8×5×3 mm were divided into 3 groups of 15 experimental blocks (repaired with 3 different composites) and 5 blocks as control group and their bond strength were evaluated under a flexural load with an instron testing machine.Results: The result revealed that flexural bond strength as follows: XR-Bond/Herculite (group 1)>Scotchbond Multi-Purpose/Brilliant (group 2)>Syntac Single-Component/Tetric Flow (group 3). Bond strength in group 1 was significantly different from groups 2 and 3, however differences between group 2 and 3 was not significant.Conclusion: Physical and mechanical Properties of composite resin are important factors on flexural bond strength. Highly-filled composite produces higher bond strength. In addition to the size of filler particles, range of the particle size, is very important. In evaluating the bond strength, stresses of polymerization shrinkage and voids are very important too. XR-Bond/Herculit system has also the ability to mature the bonds. This ability may be responsible for the higher bond strength. It seems that XR Bond/Heraclites is a proper composite for repair of this type of ceramic. Key words: Ceramic, Composite, Flexural strength