Calcium hydroxide-containing root canal sealers may encourage apical obturation by cementum. Hard-setting bases with calcium hydroxide induce calcification, but set too quickly to permit lateral condensation of gutta-percha. Since thermatic compaction requires less time than lateral condensation, the possibility of using this method with Life as a sealer was investigated. Sevently roots were prepared and filled with guttapercha using the Engine Plugger for thermatic compaction. In one group of 20 Life was used as a sealer. AH26 was used in another group of 20. The remainder served as controls. Leakage was tested by linear penetration of Procion B Blue dye measured after clearing the teeth. In the Life group the mean dye penetration was 0.575 mm versus 1.025 mm in AH26, but the difference was not statistically significant. The results indicated that Life could be used in thermatic compaction of gutta-percha and that it provided a seal comparable to that obtained with AH26.