Abstract: A process is provided which permits the rapid concentration and collection of cells in body fluid with minimal need for centrifugation and without filtration or sediment flotation, while also permitting the collection of cells from the fluid in an essentially monolayer arrangement with essentially no cell distortion. The apparatus used in this process comprises an elongated receptacle or chamber having, at one end, an outlet opening through which body fluid containing cells to be collected can be introduced, e.g., by means of a syringe, and, interposed between the inlet opening and an outlet opening at the other end of the chamber, a filter, e.g., a microporous filter.