Objectives. The aim of the present study was to compare postoperative pain on using 1.3% and 5.25% sodium hypochlorite irrigating solutions utilizing the visualanalogue scale. . Material and methods: Sodium hypochlorite solutions arerecommended as the main irrigants. This is because of their broad antimicrobialspectrum as well as their unique capacity to dissolve necrotic tissue remnants. Rootcanal treatment was completed in two visits, root canal preparation was done usingNiTi protaper rotary system. Working length was estimated by using apex locator,then confirmed with an intraoral periapical radiograph. Irrigation was done with 27-gauge needle. The root canals were obturated with gutta-percha and resin sealer usinglateral compaction technique. The patient was engaged to report the pain on visualanalogue scale before treatment, immediately after cleaning and shaping, after 3, 24,48 hours, 7days and immediately after obturation. Results: When comparing betweenmean VAS scores in the two groups, group A showed statistically significantly highermean VAS score than group B at 3, hours, 24 hours, 48 hours and at post-obturationperiods. However, there was no statistically significant difference in mean of VASfor NaOCl 5.25% and 1.3% before treatment, immediately after treatment and at 7days. Conclusions: Using NaOCl 5.25% caused more postoperative pain than1.3%.The highest incidence of pain occurs at 3 hours post operatively. Pain decreasewith time after 3 hours and disappear completely after 7 days