An in-vitro method for determining a cell type of a white blood cell in a biological sample does so without labeling, wherein a microscopy apparatus images the cell, and physical parameters of the cell are ascertained from the image of the cell by an automated image analysis. The cell type of the white blood cell is determined on the basis of the physical parameters and on the basis of principal component analysis parameters (PCA parameters) , wherein the principal component analysis parameters comprise linear combinations of at least some of the physical parameters.