This study was performed to assess the radiopacity of a variety of root canal sealers according to the specification concerning root canal sealers. Ten materials including Tubli-Seal(TM), Kerr Pulp Canal Sealer(TM), AH 26(R), AH plus(R), AH plus jet(TM), Ad sea l(TM), Sealapex(TM), NOGENOL(TM), ZOB seal(TM), Epiphany(TM) and dentin were evaluated in this study. In the first part, densitometric reading of an each step of aluminum step wedge on occlusal film was performed at different voltage and exposure time. In the second part, ten specimens were radiographed simultaneously with an aluminum step wedges on the occlusal films under decided condition. The mean radiographic den sity values of the materials were transformed into radiopacity expressed equivalent thickness of aluminum (mm Al). The following results were obtained. 1. Among the various conditions, the appropriate voltage and exposure time that meet the requirement density was 60 kVp at 0.2 s. 2. All of the materials had greater radiopacity than 3 mm Al requirement of ANSI/ADA specification No. 57 (2000) and ISO No. 6876 (2001) standards. 3. The radiopacity of materials increased as thickness of materials increased. 4. The mm Al value of each specimen at 1mm in thickness has a significant difference in the statistics. It suggests that root canal sealers have a sufficient radiopacity that meet the requirement.