A microstructured filter having an inlet for unfiltered fluid; an outlet for filtered fluid; a plurality of projections which are arranged in at least two rows in mutually juxtaposed relationship, project out of a base plate and are an integral component of the base plate; a plurality of passages between the projections and a cover plate which is securable to the base plate to cover the projections and the passages. The passages form a plurality of through paths from the inlet to the outlet. The inlet includes an elongate inlet slot for the unfiltered fluid that extends over approximately the entire filter width and is approximately as high as the projection on the outlet side of the filter.