An in vitro dye leakage study was performed to compare the apical microleakage of Ketac-Endo root canal sealer with that of Roth's 801E and AN26 sealers. Sixty-four single-rooted human teeth were instrumented and randomly divided into four groups, Three groups were obturated with laterally condensed gutta-percha and either Roth's 801E, AH26, or Ketac-Endo as the sealer, A fourth group was obturated using a single master cone and the Ketac-Endo sealer, The teeth were suspended in 1% methylene blue dye for 6 days, The teeth were then longitudinally sectioned and evaluated for linear apical dye penetration, In general, Ketac-Endo root canal sealer showed greater dye penetration than Roth's 801E and AH26, There was no statistical difference in leakage between the laterally condensed Ketac-Endo group and the single-cone-obturated Ketac-Endo group.