The primary design considerations in the application of microstrainers are discussed, i.e. the hydraulics, which determines the relative capacity of an installation, and the solids removal efficiency. Boucher's equations for the prediction of headloss through fabrics with natural waters and their application to microstrainers are discussed and analysed in the light of research work done so far on microstainers. It is also shown that the type of design criteria used with respect to solids removal efficiency includes solids character, fabric size, filterability index, peripheral speed of microstrainer and headloss.