The effect of surface-conditioning of fiber-posts on the flexural strength of the post and on the adhesion between the root dentin and cement and between the fiber-post and the composite core were assessed. The fiber-posts were subjected to cleaning with alcohol (AL), treatment with AL+silane (SIL), sandblasting with Al2O3 particles+SIL, H2O2 etching+SIL, hydrofluoric acid etching+SIL, and H3PO4 etching+SIL. For comparison, another group of specimens was left unconditioned (control group). The conditioned fiber-posts were cemented to bovine roots, and standardized cylindrical resin cores were fabricated. The specimens were subjected to 10(6) mechanical pulses and then sectioned perpendicular to the long axis of the root. Push-out tests were conducted on the sliced root sections, and microtensile testing was applied to the trimmed sliced core sections. The posts were also subjected to three-point bending tests. The surface-conditioning did not have any significant effect on the push-out strength. However, silanization increased the microtensile strength at the resin core. Sandblasting significantly decreased the flexural strength as compared to other surface treatments. Our study indicates that post surface-conditioning did not improve the post retention in the root canal, although silanization enhanced the adhesion to the core resin. Sandblasting with 125-mu m alumina particles should be avoided.