This investigation quantitatively analyzed apical leakage in teeth in which one of two new thermpolasticized gutta-percha obturating techniques were used. Apical leakage observed after use of the thermoplasticized techniques was compared to leakage found in teeth that had been obturated with conventional lateral condensation. Statistically significant differences (P 0.05) were found among the three groups. The lateral condensation group exhibited the least leakage, followed by the thermoplasticized group, and the thermoplasticized twist-off group exhibited the most apical leakage.