In this study, a comparison of the sealing properties of three different resin-based sealers, AH26, Diaket, and EndoREZ with those of the root canal sealer zinc oxide-eugenol-based U/P Root Canal Sealer was performed. Eighty extracted single-rooted human mandibular first premolar teeth were used. The coronal part of each tooth was removed at the apical 17-mm of roots. The root canals were prepared to a size 7 with Profile 0.06 taper Series 29 rotary instruments in a crown-down manner before lateral condensation of gutta-percha with the tested sealers (n = 20). A fluid filtration method was used for quantitative evaluation of apical leakage. Statistical analysis revealed that there were no significant differences between the resin-based sealers groups (AH26, Diaket, and EndoREZ) (p > 0.05). U/P Root Canal Sealer, zinc oxide-eugenol-based sealer, leaked significantly more than other tested groups (p < 0.05). Under the limitations of this study, resin-based root canal sealers were found more effective in sealing root canals than the zinc oxide-eugenol-based sealer. © 2005 Wiley Periodicals, Inc.