Objective: The aim of this study was to compare the coronal microleakage of conventional and bonded amalgam coronal-radicular (Nayyar) restorations on endodontically treated molar teeth, because coronal seal is a major factor in the long-term success of endodontic treatment. Method and materials: Forty extracted human molar teeth were root-filled and prepared for coronal-radicular amalgam restorations. Four groups of 10 teeth were restored with Tytin amalgam and Vitrebond, Superbond D Liner II, Panavia 21, or no adhesive agent. The teeth were placed in India ink for 1 week, and then demineralized and rendered transparent. The ink penetration was assessed with a coded scoring system. Results: The bonded amalgam groups produced significantly less leakage than did the nonbonded group. No statistically significant differences in leakage were detected among the bonded amalgam groups. Conclusion: To prevent the reinfection of the endodontically treated molar, it may be preferable to restore the tooth immediately after obturation by employing a bonded amalgam coronal-radicular technique.