Countercurrent elutriation is a powerful method for fast and gentle large-scale isolation of cells according to size and density. Current limitations of this approach are the suboptimal selectivity that is obtained and the fact that the total number of cells that can be separated per run is restricted. We describe a new separation chamber, which was calculated according to the hydrodynamic boundaries of the counterflow separation. In comparison to the chamber commonly in use, a fivefold higher cell number can be separated with this chamber at an increased separation selectivity. Furthermore the use of this chamber, which fits to the standard Beckman equipment, avoids large sampling volumes.