Objectives: The aim of the present study was to evaluate the efficacy of R-Endo and D-RaCe Retreatment instruments with and without using passive ultrasonic irrigation on the removal of root canal filling material, and the time required for its removal. Materials and methods: Sixty mandibular premolars with single canals were decoronated; the root canals prepared using the Revo-S rotary system and obturated with gutta-percha size (25/.06), using lateral compaction technique. Roots were divided into four equal groups (n = 15) according to the retreatment rotary system and the final irrigation technique used in the removal of root canal filling material into: R-Endo retreatment system with conventional irrigation (R-Endo/C), R-Endo retreatment system with passive ultrasonic irrigation (R-Endo/PUI), D-RaCe retreatment system with conventional irrigation (D-RaCe/C) and D-RaCe retreatment system with passive ultrasonic irrigation (D-RaCe/PUI). Roots were split into two halves longitudinally and the canal walls photographed using a digital camera connected to a stereomicroscope. The remaining filling material in each root canal third was evaluated using Image-J software. Data were analysed using the Mann-Whitney U test for the rotary system comparisons and irrigation techniques, while Friedman's test was used to compare between the different root canal levels. Results: There was a statistically significant difference in the total area percentage of the remaining filling material among the four groups (P 0.05). The D-RaCe/PUI group showed the least amount of the remaining root canal filling material, followed by R-Endo/PUI, then D-RaCe/C, while the R-Endo/C showed the highest amount. Conclusion: D-RaCe/PUI group was the fastest and the most efficient technique in the removal of the root canal filling material. Keywords: D-RaCe, passive ultrasonic irrigation, R-Endo, retreatment, stereomicroscope The authors declare that they have no conflict of interest.