Aim of the study To evaluated the effect of working length determination using electronic apex locator or digital radiography on postoperative pain and amount of analgesic intake in patient with a symptomatic irreversible pulpitis due to carious exposures or normal pulps treated for prosthetic reasons.Steps:54 patients were enrolled in this study, randomized and allocated to the two experimental groups (27 each). Where access was done then working length measurement determination was done according to the allocated group, chemomechanical preparation was performed by Protaper universal files, irrigation was done with 2.5% NaOCl and obturated by modified single cone technique and ADseal. The patients were instructed to record the postoperative pain readings in a given chart at specific time intervals 4,6,12,24,48 hours and 7 days, the number of days needed by the pain to disappear was also recorded and the number of analgesic tablets taken by the patient in the specific time intervals.Results:There was no statistical significant difference between the two groups regarding the postoperative pain levels, duration or the number of analgesic tablets intake, However, there was a statistical significant difference between different time intervals in the same group with 4 & 6 hours intervals having the maximum degree of postoperative pain.Conclusion : There is no difference in postoperative pain level or amount of analgesic intake when either apex locator or digital radiography is used for working length determination in multirooted teeth. However, the use of apex locator may provide the benefit of radiation dose reduction which is beneficial for the patients and follows the ALARA principle.