The research presented in this study compared the effect of two types of reinforcements, glass fiber post and metal mesh, on the fracture resistance of three unit's interim fixed partial denture. Also, two sites of reinforcements were selected, at the connector part and in the cervical part of the pontic, to determine the optimal position for interim fixed partial denture reinforcement.A total of fifty resin samples of three units fixed partial denture were constructed for the test using a chemically cured interim resin material (Cool temp Natural) and were divided into five groups (n= 10) according to the reinforcement type and location as follows: Group (A), no reinforcement; Group (B), glass fiber in the occlusal part; Group (C), metal mesh in the occlusal part; Group (D), glass fiber in the cervical part of pontic; Group (E), metal mesh in the cervical part of pontic.