- Useful when density of microfilariae is low - Uses Swinney membrane filter where microfilariae is recovered - Membrane filtration recovers most species of microfilariae; however, because of their small size, Mansonella perstans and M. ozzardi may not be recovered. - This is the most sensitive method of detecting small numbers of microfilariae, but it is expensive for routine use. - The blood is passed through a polycarbonate filter that contains a 2-μm pore. - Distilled water is passed through the filter, lysing the red blood cells and improving the visualization of the parasites.