The aim of the present study was to evaluate microleakage of three root end filling materials; MTA, Amalgam and Resin bonded composite after its exposure to a range of different pH environments. values of 4(acid), 7(neutral), or 9(alkaline) for 3 days . Microleakage was evaluated by using bovine serum albumin. The evaluation was conducted at 10 days intervals for 80 days. amalgam the greatest leakage was observed in alkaline, acidic and neutral respectively. While for composite greatest leakage was observed in an acidic, neutral and alkaline pH respectively