This study compares the in vitro apical seal achieved with thermoplasticized gutta-percha used with and without a sealer cement and that achieved with dental amalgam and a varnish liner following an apicoectomy and a Class I preparation of single root teeth. The teeth were immersed in methylene blue dye for 10 days, were sectioned longitudinally, and the amount of leakage was determined. No difference in leakage was found between the apical seals achieved with thermoplasticized gutta-percha used with a sealer cement and that obtained with dental amalgam with varnish. The leakage found with thermoplasticized gutta-percha used without a sealer cement was significantly greater.