Objective: The purpose of this study was to evaluate the fracture resistance and the mode of failure of endodontically treated teeth restored with four post-and-core systems. Method and materials: Forty intact human incisors were randomly divided into four groups. Teeth from each group received endodontic therapy and one of four post-and-core systems: serrated, parallel-sided, cast post and core; serrated, parallel-sided, prefabricated post and resin-composite core; carbon-fiber-reinforced (CFC) post and resin-composite core; and ceramic post and resin-composite core. A full-coverage metal crown was fabricated and cemented onto each tooth. Each specimen was subjected to a compressive load at a 45-degree angle to its axis until failure. The failure load was recorded and compared statistically. The mode of failure of the specimens was analyzed. Results: There was no significant difference in the failure loads among groups. More catastrophic root fracture was detected in the group restored with ceramic posts and resin-composite cores. Conclusion: The fracture resistance of endodontically treated teeth restored with these four post-and-core systems could be accepted clinically. Unfavorable tooth fracture was shown in all groups.