The purpose of this study was to determine the fracture load for three different core materials supported by three different post systems. The study was divided into nine separate groups, and each group comprised 10 samples. Specimens were placed in a special jig on a 45-degree angle, and the fracture load values were obtained using a universal testing machine. A 3 x 3 factorial two-way analysis of variance (P .0408) was used to test the effects of core material and post type on the fractural resistance. Fracture load values (as measured in pounds) were: Flexi-Post/Ti-Core, 204.9; Vlock/Ti-Core, 218.8; Parapost/Ti-Core, 164.8; Flexi-Post/Tytin, 156.0; Vlock/Tytin, 100.6; Parapost/Tytin, 134.6; Flexi-Post/Ketac-Silver, 69.4; Vlock/Ketac-Silver, 50.4; and Parapost/Ketac-Silver, 37.7. The titanium composite, Ti-Core, had the greatest fracture load values in all instances; the silver-filled glass-ionomer specimen, Ketac-Silver, had the least. The Flexi-Post and the microthread, Vlock, had the greatest fracture load values, and the Parapost had the least. Both the Flexi-Post and Vlock post have large bulky heads with many vertical and horizontal grooves, apparently facilitating the locking of the core material into the post.