This study was carried out to compare the efficacy of wastewater treatment by activated sludge and EM(Effective Microorganisms). The sequencing batch reactors were fed synthetic wastewater and operated on a cycle consisting of the following phases: 30 min fill, 3 hr anaerobic, 14 hr aerobic, 4 hr anoxic, 2 hr settling, 30 min draw. Nitrogen and phosphorous removal efficiency were about 98%, 92%, respectively in the EM-received reactor. The almost identical performance achieved with EM in comparison to activated sluge.