Abstract: A method of multi-color labeling at least two antigens present in a tissue such as non-liquid tissue or body fluids, with the aid of different antibodies is improved by introducing between the labeling of the first antigen and the labeling of the second antigen, and between labeling of the second and that of any further antigen, at least once a treatment with a non-immune normal serum and optionally other agents blocking any binding sites remaining free in the tissue after a last-preceding labeling step.