This study was conducted to evaluate the influence of immediate versus delayed immersion time, and passive dye immersion versus centrifuged dye on apical leakage measurements. Eighty-four extracted human teeth with single straight canals were instrumented and divided into four experimental groups of 20 teeth each plus 2 negative and 2 positive controls. Low-temperature injection thermoplasticized gutta-percha and sealer were used to obturate the root canals. In groups A and B the filling materials were allowed to set for 72 h before the teeth were placed in India ink. In groups C and D the teeth were placed in India ink immediately after obturation. Also, in groups B and D the teeth were centrifuged in India ink for 20 min at 3,000 rpm before being immersed in ink. After 72 h in India ink, the teeth were cleared, and the linear extent of ink penetration was measured with a stereomicroscope. Statistical analysis of the data revealed no significant difference in leakage among the experimental groups whether the teeth were immersed in ink immediately after obturation or after setting of the filling materials for 72 h, and whether or not the teeth were centrifuged in ink prior to immersion.