1.1 ,This test method, provided the limitations are understood, covers a procedure for both the enumeration and measurement of size distribution of most all cell types. The instrumentation allows for user-selectable cell size settings and is applicable to a wide range of cell types. The method works best for spherical cells, and may be less accurate if cells are not spherical, such as for discoid cells or budding yeast. The method is appropriate for suspension as well as adherent cell cultures (1).2 Results may be reported as number of cells per milliliter or total number of cells per volume of cell suspension analyzed. Size distribution may be expressed in cell diameter or volume.