Operating characteristics for an ultrasonically assisted filtration technique applicable to micron to millimeter-sized particles suspended in liquid have been studied. The technique uses a highly porous filtration medium having pores up to two orders of magnitude larger than the particles being collected. When a resonant ultrasonic standing wave field is applied to the medium, the particles become trapped on the elements comprising the porous medium or within its pores. The test suspension consisted of 325-mesh polystyrene particles in water. The porous medium was a polyester mesh containing 30 pores per inch (the nominal pore size is 847 mu m). Filtration efficiencies ranging from 60 to 85% have been observed. The effect of flow configuration on filtration efficiency and two approaches for cleaning of the mesh have been examined.