Abstract: An apparatus for automated classification of white blood cells comprising photo-electric converter means whereby the green and blue lights passing through the blood smear are converted into the respective electric signals, a first means for detecting the zone where the nucleus of white blood cell is present at a certain threshold level determined by the maximum and minimum values of the electric signal corresponding to green color, a second means for discriminating between the nucleus of white blood cell obtained from said first means and the granules and cytoplasm of white blood cell at a certain threshold level determined according to said electric signal corresponding to green color, a third means for discriminating between said cytoplasm and the back-ground at the threshold value determined on the basis of said electric signal corresponding to green color and obtained by adding a certain value to the average density on the back-ground, and a fourth means for discriminating between said nucleus and the red

Abstract: A method wherein at least one standard leukocyte is selected from within a blood film in advance, the values of adjustments are calculated on the basis of the differences between a plurality of characteristic parameters evaluated from the standard leukocyte and the corresponding characteristic parameters previously given, and the characteristic parameters of the other leukocytes in the particular blood film are adjusted with these values of adjustments. Further, using the adjusted characteristic parameters, secondary characteristics are derived.