Two methods for the specific visualization of granulocytes (PMNs) in formalin-fixed and paraffin-embedded tissue samples were compared: (1) the well-established enzyme histochemical method using naphthol-AS-D-chloracetate as a substrate; (2) an immunoperoxidase reaction using anti-PMN serum. Both methods are highly selective for visualizing PMNs. The advantages offered by the immunohistochemical method, i.e. better visualization of the remaining tissue structures and potential combination with other staining techniques, are stressed. Problems of PMN visualization in lung tissue and effects of tissue preparation are discussed. For histomorphometric studies the immunohistochemical method is preferable.