AbstractCurrently used classifiers for flow cell sorters are described and the look‐up table is introduced as such. An experimental setup of a look‐up table classifier added to a commercially available cell sorter, under control of a microcomputer is described. The contents of the look‐up table are obtained from contrours of regions of interest. These regions are defined by the user who designates the areas on a video color display of the bivariate flow data. Since most cell clusters form elliptic or ovoid shapes in a multi‐dimensional feature space this method enables a better matching of window shapes to cluster outlines, compared to conventional sort decision circuitry.