The simulation of a system to perform an automated leukocyte differential has been achieved through the measurement of certain features or parameters on the cell image. Using photomicrographs on Kodachrome II-A film of Wright's stained leukocytes, the following four features have successfully separated five normal cell types (neutrophil, eosinophil, basophil, lymphocyte, and monocyte): 1) nucleus size; 2) nucleus color; 3) cytoplasm size; 4) cytoplasm color.