Objective: The aim of this in vitro study was to compare the various techniques for removing precipitate formed after irrigation with sodium hypochlorite (NaOCl) and chlorhexidine (CHX). Background data: It is still unclear whether different irrigant activation systems can effectively remove precipitate that is firmly attached to the root canal walls. Methods: Eighty-two extracted single-rooted human teeth were instrumented by using the ProTaper rotary system. The roots were irrigated with 5% NaOCl and then 2% CHX to form orange-brown precipitate on the root canal walls. The teeth were sectioned longitudinally, and the amount of precipitate on the canal walls was measured under a stereomicroscope at 15xmagnification before the root halves were reassembled. Then, conventional syringe irrigation (CSI), CanalBrush (CB), EndoActivator (EA) system, photon-induced photoacoustic streaming (PIPS), and manual instrumentation (MI) techniques were used to remove the precipitate, during which 5mL of distilled water was used for 1min. The amount of precipitate remaining on the canal walls was measured, and the percentage of precipitate removed was calculated. Data were analyzed by using the Kruskal-Wallis and Mann-Whitney U tests (p=0.05). Results: All experimental groups contained residual precipitate. The precipitate was more effectively removed in the MI group than in the other groups (p<0.05). The CB and EA groups showed better removal than the CSI and PIPS groups (p<0.05), and there were no significant differences in removal between these latter two groups (p>0.05). Conclusions: None of the techniques used was able to completely remove the orange-brown precipitate from the root canal surfaces.