Restoration of endodontically treated teeth is a routine procedure in everyday clinical practice. Placement of posts and cores is often required for replacement of the missing coronal aspect of teeth. Use of traditional post-and-core systems (gold and titanium) in conjunction with all-ceramic restorations results in poor esthetics because of the reflection and lack of light transmission. For a highly esthetic outcome, there is a need to use a material that transmits and refracts light in much the same manner as a natural tooth. The purpose of this study was to clinically evaluate the light transmission of a (1) ceramic post (Celay),(2) polyester post reinforced with zirconium fibers (Snowlight), and (3) zirconia post (Cosmopost), in comparison with a cast-metal post and core covered with opaque porcelain (control). The light transmission of these systems when used in conjunction with IPS Empress all-ceramic crowns was evaluated.(Int J Periodontics Restorative Dent 2004; 24: 462–469.)