The present study aimed to compare the ability of different types of posts to reinforce endodontically treated teeth by evaluation of the fracture resistance of the reinforced teeth.Fifty six intact human central incisors were endodontically treated by lateral condensation technique using hand file instruments. The teeth were divided into seven groups and then six groups were prepared to receive different types of posts using special drill supplied with post manufacturers while the last group was left as a controlled group.The posts were then cemented to their prepared root canals using RelyX Unicem resin cement. All teeth after that were mounted in plastic tube full of acrylic resin. For standardization mean the cementation load, a specially constructed cementation device, was used to apply a constant load (3kg) on the cemented posts during setting for 5 minutes.Posts then cut using disk and round burs to be extended 2mm. in the pulp chamber.The core was then built into each tooth including the controlled group using light cured composite resin.Teeth with their post-cores were then divided into seven main groups according to the type of the post used to reinforce the teeth.Group (1): eight teeth reinforced by zirconia posts.Group (2): eight teeth reinforced by RlyX fiber posts.Group (3): eight teeth reinforced by carbon fiber posts.Group (4): eight teeth reinforced by costume made posts.Group (5): eight teeth reinforced by titanium posts.Group (6): eight teeth reinforced by mixed posts postsGroup (7): eight teeth left without post reinforcement.Each specimen will then be positioned in a mounting device to be aligned at a 45 degree angle with respect to the long axis of the teeth. Specimens will be placed on the universal testing machine and the load will fall on the cingulum of their palatal surfaces at a cross head speed of 1mm/minute . The load at which fracture of the cervical part occurs will be recorded as the fracture resistance. Specimens were then assessed using scanning electron microscope at 500x and 1000x magnification.The results revealed that, some types of post used in this study can reinforce the teeth while others can not reinforce the teeth compared to the controlled group which is left without posts.It was found that Rely X post group recorded statistically significant highest fraucture resistance mean value followed by Titanium post group then Mix post group , Zr post group , Carbon fiber post group, Gutta percha group, while Custom made post group recorded statistically significant lowest fraucture resistance mean value as indicated by one way ANOVA. Pair-wise Tukey’s post-hoc tests showed non-significant difference between (Rely X post, Titanium post, Mix post, Zr post). Also Tukey’s post-hoc tests showed non-significant difference between (Carbon fiber post, Gutta percha and Custom made post).Electronic scanning microscope was used to evaluate the mode of failure and type of fracture in each group.