Objective: The purpose of this study was to assess three modern root-end restorative materials with electrical and dye leakage tests. Method and materials: Thirty-three human canine teeth were prepared and filled with gutta-percha and sealer. Stainless steel rods were inserted into the root canals as anodes, and the teeth were varnished. The apical 3 mm of each tooth was resected, and 3-mm root-end preparations were made ultrasonically. Mineral trioxide aggregate, Super EBA, and IRM were used to restore 10 teeth each, and three teeth were varnished as controls. Following 24 hours' setting in blood, the specimens were placed in 1% potassium chloride electrolyte, and leakage was recorded electrically for 70 days. The teeth were then submerged in methylene blue dye for 72 hours, sectioned longitudinally, and scored for leakage by six examiners. Results: In both tests, the mineral trioxide aggregate restorations leaked significantly less than the IRM and Super EBA restorations. Super EBA showed significantly less leakage than did IRM restorations in the electrochemical test but not in the dye leakage experiment. The teeth sealed with mineral trioxide aggregate performed similarly to the varnished negative control teeth. Conclusion: The results of this study indicated that mineral trioxide aggregate provides a superior seal in root-end restorations.