Because fine particulate matter 2.5 mu m in diameter (PM2.5) causes health problems, PM2.5 emissions are of concern. However, little research on stationary sources has been conducted. To determine the concentration and filtration behavior of PM2.5, dust was collected from five fluid-bed sewage sludge incinerators (SSIs) sorted by particle size using cascade impactors. The average PM2.5 concentration was 0.00014-4.8mg/Nm(3). The total estimated amount of PM2.5 emissions from the SSIs for all plants in Japan was 0.96-8.9tons/year. Since the SSIs with dry Electrostatic Precipitators (EP) contributed 75-99% of the total emissions, replacing dry EPs with bag filters would significantly reduce the PM2.5 emissions from SSI.