Two SBR reactors were operated with feed of domestic sewage (Run-S) and enriched sewage with particulate organic matters (Run-SP) until stable EBPR process was developed, while the third reactor was fed with acetate (Run-A) for a reference. Microbial community of activated sludges was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method. Based on the analysis of DGGE band patterns, three bands were found commonly in all the lanes. Four bands were common between Run-A and Run-SP. There was no remarkable difference in band patterns between Run-A and Run-SP, which indicated that the addition of POM did not affect significantly the microbial community change in the activated sludge. The DNA sequences of the bands C1 and A/SP corresponded to the related sequences of Thiothrix sp. and Rhodocyclus sp., respectively.