Objective: The present study was performed to evaluate of postoperative pain in mandibular first molar after instrumentation with different files metallurgy with different motions with or without activation of irrigant. Methods: 60 male that need root canal treatment for their mandibular first molar were dividing to six groups. Group A1B1: Instrumentation using XP endo Shaper with activation using XP endo finisher. Group A1B2: Instrumentation using XP endo Shaper with traditional side vented needle irrigation. Group A2B1: Instrumentation using 2Shape files with activation using XP endo finisher. Group A2B2: Instrumentation using 2Shape files with traditional side vented needle irrigation. Group A3B1: Instrumentation using Reciproc Blue with activation using XP endo finisher. Group A3B2: Instrumentation using Reciproc Blue with traditional side vented needle irrigation. Then evaluate the postoperative pain at 12, 48 and 72 hours. Results: Results of the study showed that the highest mean pain score value was recorded with Reciproc blue at all intervals while activation of the irrigating solution , the results showed dramatically decrease in the postoperative pain level when XP finisher was used following root canal instrumentation using Recioproc  blue. Conclusions: Reciproc blue reciprocating file induces postoperative pain than XP endo shaper and 2Shape continuous rotation systems.