Objectives: This laboratory study compared the effects of various post systems on the fracture resistance of endodontically treated mandibular premolars. Method and materials: Thirty-two extracted mandibular first premolars were collected, endodontically treated, and assigned into four test groups (n = 8). The classification was based on the post material as follows: traditional glass-fiber posts (TFP), traditional titanium posts (TTP), coated glass-fiber posts (CFP), and coated titanium posts (CTP). The posts were cemented with a dual-curing luting composite resin. Each specimen, which was prepared with a 2-mm ferrule height, received a composite resin core. All specimens were restored with cast CoCr crowns, which were cemented with glass-ionomer cement. All specimens were submitted to dynamic loading in a dual-axis chewing simulator for 1,200,000 cycles with a nominal load of 5 kg and simultaneous thermal cycling (5 to 55°C). Each specimen was secured in place and loaded at 30 degrees using a universal testing machine until fracture occurred. The results obtained were analyzed using one-way ANOVA and the fracture modes were investigated under stereomagnification (25×). Results: Fracture loads were as follows: 858 ± 216 N for CTP, 953 ±134 N for TFP, 979 ± 219 N for CFP, and 1,130 ± 286 N for TTP group. One-way ANOVA revealed no statistically significant differences among the test groups (P = .112). Conclusions: Under the conditions of the current study, no significant fracture resistance differences were found between teeth with the different prefabricated post systems. Keywords: endodontically treated teeth, fracture resistance, glass-fiber post, resin cement, titanium post